As a former 3010 owner (3020 is same plus wireless hdmi), the lag is quite noticeable in any twitch games. I didn't play a lot of that style so it didn't bug me much, but when I did try I found it miserable. 60ms was the minimum I was ever able to measure.
When I moved I made sure to get something much lower lag.
By comparison so far I'm extremely happy with my hd25-lv. I've been specifically trying to find instances where I could detect lag, and so far have not found any. Haven't measured it though.
The Benq 1070 was also on my preferred list, but I decided on the hd25 because the -lv version will combat our living room ambient light better. Only reason to prefer the 1080 (as far as I'm aware) is if you want the short through specifically.
750 is actually lower measured lag than even the hd25, and much lower price, but you give up 1080p.
The 8350 is pretty much zero lag, and moderate on the lumen scale, but I think of the options above it probably has the general best reputation for good 2d picture. No 3d at all though.
If you're talking about the newly released viewsonic 1080p 3d, that is a great-looking little projector - super-bright, 1080p, 3d, inexpensive, perfect package .... but the reviews haven't been overly impressed with picture quality so far. Seems like this might be the perfect gaming projector, but maybe not as great on movies.
On the warranty, I have no idea what the best buy warranty does for you. I will say this, though -- my experience with Optoma's warranty service has been very poor - nearly a month turnaround on a projector that was less than a month old when I sent it in, and they were pretty much completely unapologetic. They basically stated their process was consistent with industry standard though, and I've not dealt with any other company processes, so they may be completely honest there.