This is more of a hypothetical question, but most likely I'l be editing in Final cut studio on a Mac (New Imac or MacPro). Output should be good enough for web and broadcast.
Just so you know, I am going to buy an HDtv along with an PS3, and was just wondering if I could use the 800+€ device for work as well as play....
Even if you can use the HDTV as a computer monitor, it's not the same thing as outputing to via an HD input/output card (may require the MacPro). If you output using the output card, then you'll be seeing a true HDTV picture (colorwise) and it will look as acurate as your HDTV can display it...
If you use the HDTV as a computer monitor, you'll be watching a quicktime version which will be less color accurate for HDTV use, but good for web use. Make sure you set your mac display setting to gamma 1.8 in the monitor preferences when viewing quicktime video (including thru FCP) as Quicktime is not colorsync aware like photoshop.
The good news (I think, haven't tried it) is that if you can use your HDTV as a computer monitor you may be able to calibrate it using something like the EYEone Display device. And the pre-cal section of the software will guide you to proper set up of the monitor itself through the monitor menus on the TV. This should make your HDTV accurate for normal HD viewing without the computer which is pretty cool. My pro HD monitor doesn't have DVI input, so I can't do this so easily (only HD SDI).
The downside to the consumer hdtv is that if you get an HD input/output card, it might only have HD SDI output/input and not DVI or HDMI for the consumer TV so you'll have to check that out. If you get an iMac, this option may be closed to you anyway, but there might be some new firewire converter or some such thing you can use that I don't know about...
Lastly, If when you set up your TV menus, don't set it to "sports" or "vivid" or those settings. Usually something like "cinema" settings will turn off all/most of the image enhancements that come on with the other settings.
Best of luck with it!