Widescreen gaming will pretty much spoil the heck out of you with a HiDef TV, gaming on a small screen will never be the same.
The drawbacks of gameplay depend on whether the game you want to play in, will run in the resolution your TV will run at, sometimes gameplay may require you to drop to 800 x 600, but thats because your widescreen has limitations.
My highest res on the 27" I was using was 1280 x 720 which admittedly gave me quite a few Oohs and Aahs in the beginning playing games like FarCry which can cover pretty much any resolution you want to play in, but ran into serious limitations with other things I wanted to do.
I'm not trying to discourage you just share some things I've learned from my own experiences if I had a 30" LG I'd have been ran that sucker.
Another important point is the response time of the monitor the faster the response the better for gaming especially in a FPS [First Person Shooter] game, too high of a response time gives smears turning corners and is literally unplayable.
Response time like 25ms is way too low, 16ms is pretty much borderline towards the Not side but still playable, 12ms is doable, 8ms is pretty much on the money, and below 8ms is pretty much awesome, this is my personal opinion here OK, someone will surely post how great their monitor performs and how dumb my opinion is, but thats to be expected here.
My early LCD gaming days involved many monitors that went back to the store until I found response times that worked flawlessly for FPS gaming of which I am a DieHard addict, FPS is my gaming choice period.
Hopefully you have a DVI input on the monitor and DVI output on the computers video card, simply because if you can go that route from my experience your resolution sets to your exact screen parameters, eliminating having to adjust the screen to fit.
And if the LG has DVI input its going to be a better performer relating to computer use, the higher performing monitors/HDTVs usually have both inputs, DVI and VGA, VGA input is the most common connection for computer use.
I'm running 7800GTX graphics cards in SLI, but singly they still perform with any game I play on the maximum resolution I want to run at.
Futurewise I cannot comment on 7800s lastability, but for anything [gamewise] on the market today with WinXP they are still top performers as far as gameplay is concerned.
I know you're going to have a blast gaming on a 30" widescreen and I'm kinda excited for you, I eventually went to a 24" instead of the 27" I was using, because I was after higher resolutions gaming and now run in 1920 x 1200, but I still remember how awesome it was when I first fired up the 27" playing FarCry in 1280 x 720.
I don't know what kind of games you like to play but you'll love it.