The reason people buy lcds for bright rooms is that they can get much brighter than plasmas.
I'm not exactly crazy about this reviewer and must admit that I know little about him. But this may be an example of one of the reasons why, before your quote he stated the following, which doesn't exactly support his recommendation:
The one caveat to this is that the Samsung is limited by the amount of light it can put out in the only good picture mode, Movie, so contrast and pop aren't quite as good as on the Panasonic plasmas we've tested.
When he said that the ST50 was slightly grey, I have to wonder what state it was in when he viewed it, where it was in relation to the Samsung, etc. Having owned a GT50, I find his recommendation hard to believe since when watching Game of Thrones during the day I saw no evidence of gray that was not accurate. I posted a few pictures taken during the day on the GT50 thread if you'd like to take a look.
In addition, this review seems to indicate that the 3D isn't very good at all.
I'm not understanding why one would want to limit their viewing to only "one good picture mode" either, unless of course one has a controlled environment. Bright rooms are not always bright. D-Nice has stated that he can get a second satisfying mode from the ST50.
However, if that tv meets your needs it sounds like it's a good buy.