Frankly I've never met a 50mm I haven't liked. There may be subpar designs out there, and certainly you can run into subpar samples of some designs, but I don't think I've ever sold or given one away. (I did regrettably lose an FD mount Canon in the Nile river in 1984 and more recently smashed an EF Canon to bits after one too many AF miscues...but optically the smashed lens--which, BTW, more than deserved its fate--was quite fine.) Even weird-ish pre-WWII designs like the Leitz Summar have their charms.
If you're a smooth bokeh aficianado you'll likely find most 50s to be squirrely at times. Depends on aperture, how far away from the plane of focus the out-of-focus areas are and what the structural nature of the OOF stuff is.
As for reviews, most of what I've seen comes from enthusiast sites or blogs and tends to be positive. Maybe that's due to brand loyalty, or maybe it's because no-one has made a bad 50 in a good long time. 50s tend to be inexpensive, so you're probably best off just trying one from your maker of choice.
(I'm most partial to the Zeiss 50/1.5 Sonnar, along with its Soviet-era Jupiter clones, made primarily for Contax rangefinder cameras. It's, by modern standards, a medium to low-ish contrast lens. Has a signature, mostly unobtrusive texture in OOF areas. Gives me a good reason to keep using b&w film.)
-Dave-
