I laughed when I saw this post, because in the LL forum community, asking whether to consider a Sony is akin to being in the Vatican and openly pondering whether Catholicism is a worthwhile religion.
That being said, being the equivalent of an orthodox jew in a seventh day adventist church and thus totally out of favor given I'm a Nikon user in a foreign land here, I will offer my answer and it's real simple: No, I won't buy a Sony. They're not horrible cameras by any means, but I have my own reasons, based upon a multi-decade experience with many brands and formats.
a) I don't like and never liked Minolta reliability. Guess who Sony bought. I've been shooting for over 30 years. Over that time, without question, the number one brand that repeatedly time and time again seems to give people reliability issues that myself and my colleagues have witnessed is Minolta. If it had been just once or twice that I had to listen to your basic mom and/or pop who saw me with my expensive gear and tell me how their Minolta (of anything from SRT vintage to Maxxum and beyond) broke down, I'd say it's just luck of the draw, but when you hear it consistently over a few decades, I tend to think that's a trend. You don't see the guys whose living depend on the gear shooting Sony, and I think that's part of the reason. That doesn't mean it's junk, but I do think it means they've got reliability issues when the gear is pushed. Perhaps Sony has addressed these and I hope for the Sony fans they do, but this is one aspect I'm not interested in dealing with. I need a reliable system and Nikon, in 30+ years, has never let me down, and I've beat the hell out of their gear. My colleagues with Canon tend to feel the same way. In my mind, if you're serious, it's a two player race, and it's for a reason. Proven performance and reliability over time.
b) You buy into a camera system, not a particular body. Even if the Sony stuff were to be perfectly reliable, I still find their system limited. Sure, the Zeiss glass is nice, but so is other glass (see item 'c' coming next). But I need a 200/2 for stage and theater work when I get it. Oops. Can't find that in Sony (or Pentaxes) system. It is in both Nikon and Canon systems though. Top tier tilt-shift lenses. Same thing. Got a few choices in Nikon and Canon. A fully evolved flash system. Once again, a Nikon strength. Over time I need to know that the system I buy into is going to be around, and produce the gear I need. Two players have a dominant position in the marketplace, and frankly, those are the only two players I consider for this reason. Sony hasn't even gained substantial market share even after cutting the prices of their 24mp full frame bodies. They haven't publicly committed to growing their full frame bodies. Sorry, but I want no part of this. I need someone who is going to be there in the future for me, not the "alternative" camera for the folks who sneer at the major players and want to play contrarian.
c) Lenses? Sure - for a while, the Zeiss stuff might have held an edge - if they had a lens in the focal length range you needed, which isn't always the case. This has started to change. Newer glass like the Nikon 85/1.4G or the 24/1.4 and 35/1.4 G lenses will match up quite well, and IMO in some aspects, particularly OOF rendering, are superior to, anything Zeiss (or anyone else) currently offers. The new Canon 17 TS is amazing, and the Canon 70-200/2.8 L-II is a monster, a wonderful, wonderful lens. Thing is, the big boys know that the limiting factor in the equation with all these high resolution bodies that have come down the pike, even bodies like the affordable Nikon D7000 or the Canon 7D, is the quality of the lens. It's no surprise that the latest efforts from Nikon have been supremely excellent, as have several of the latest "L-II" options from Canon. The newer glass from the two major players is simply better, as it needs to be, than the older stuff. This diminishes the supposed "Sony/Zeiss" advantage.
Plus I laugh at all these folks who pixel peep comparing sharpness of their Zeiss vs Canon or Nikon lenses, looking for tiny bits of sharpness advantage, never realizing that a) the dot gain of the printing process often masks much of this supposed advantage, and b) unless they are shooting in lab-like conditions on a top tier tripod/support system, have learned how to sharpen and post process properly, and are shooting in clear atmosphere, that this sharpness obsession isn't going to be realized in real life shooting. It's funny - just to take a non Nikon guy so I don't appear too Nikon biased - look at what Art Wolfe (A Canon shooter) shoots with - and the results he gets out of it - and tell me straight to my face that he needs to dump all his gear and only shoot Sony/Zeiss or Zeiss glass? I call Bulls**t on that. Most pros do well with the basic configuration of the pro 2.8 zooms and a few selected primes plus a long exotic or two, and produce excellent work from this. I'm not arguing that good glass isn't essential - but at the current time, there is no significant across the line advantage to the Sony/Zeiss lineup that makes it uniformly better than the best Nikon or Canon has to offer, particularly when real life usage is taken into account. Maybe if you're into photographing resolution charts and comparing review graphs to prop up your self esteem of what camera brand you bought, but not for those out there taking real images.
So you want to buy a Sony - go ahead, they're not bad cameras at all, and heck, they're reasonably priced. A couple of those Sony/Zeiss lenses are really special (the 135/1.8, if you can get it focused spot on). But you asked if I would ever buy one, and the answer is no. They're not a major player, aren't likely going to be one in the professional space, and thus, I want no part of them. I'm a Nikon guy, but if I had to, I'd go Canon and not lose a whole lot of sleep over it. Both of those brands have complete systems, are dedicated to their lineups and advancing them, and have been proven over time. Sony can't claim that. Perhaps when the Art Wolfes, Jay Maisels, Bill Frakes, Walter Iooss's of the world are all shooting Sony and Nikon/Canon has been relegated to the bit player role, I'll have a different opinion. But it hasn't happened, probably isn't going to happen, so I'll stay with the big players for now.
(As an aside, do you know why the D700 is so popular amongst Nikon users? It's because it's a balanced design that has enough resolution for most real world applications, can shoot in a damned cave if you need to, has an AF system that can track whatever it has to, has files that can be manipulated and massaged to no end in post processing, and ultimately is a camera that lets you concentrate on creating images as a photographer instead of being a gear head - it gets out of your way the way a truly good car lets you concentrate on the road you happen to be driving on. I wouldn't give mine up if you gave me a pair of A900's for free)