1) From what I've heard, the G15 is essentially identical to the G10, except the top half of the set is thinner---around 2 inches wide. Thinner form factor, at least for the top half of the TV.
2) The Cinema Smooth on the B650 does not work properly, and I wouldn't hold out much hope that Samsung is going to fix it--but you never know. The 48hz on the G10 doesn't work very well either, so I guess there is no incentive for either to fix their 24p implementation if their competition doesn't fix theirs either.
3) It's proper to say, "would have gone," and incorrect to say "would have went". Always watch out for those past participles! "I went..." becomes "I would have gone..." Don't take it personally. I notice in the message above, after I posted, that I accidently slipped in an extra s when I spelled "plusses," which I should have spelled with one s as "pluses".
4) If you are hyper-sensitive to IR issues, go with one of the Japanese manufacturers like Panasonic or Pioneer. The Korean makers (LG and Samsung) are not as good in this area.
I would buy a Panasonic PDP before going with the smaller Samsung LCD. Panasonic makes a quality plasma that most people are quite satisfied with. So what, their colors are not perfect. But they do have noticeably better blacks than the Samsungs.
The G10 will not look good in the bright lights of the store. It washes out a bit faster under the harsh lighting than the B650, because its filter is not as dark. Go look at one in a more moderate environment and the G10 will fare much better. What do you want for 50 inches at less than $1200?
In the high end section of my local Magnolia there are two walls adjoining one another, and one wall opposite, which have a total of 25 TV's lit up on them. I counted how many downward firing incandescent ceiling lights they have recessed into the ceiling. There were a total of 17 (!) of them and they were 70 watt lights. Granted, they were obviously not running at full brightness. Perhaps they were only running at 25% brightness or something like that. But even with all the light from the 25 TV's in that section that was being reflected, along with the 17 lights, the lighting is still more moderate than Sears, Best Buy, etc. But it's by no means dark. And in this setting the blacks on the G10 looked a bit darker than on the Samsungs.
So TRUST ME, when you get the G10 home and away from the bright lights, and you watch in a normal viewing environment, the blacks on the G10 will have no trouble surpassing that of the Samsungs. In a dark room you will easily be able to tell the difference.
Perhaps I should upload some screenshots from the 2009 HDTV shootout to demonstrate the difference in a dark room.