LCDs can have slight tradeoffs as PC/gaming monitors. Ones without 4:4:4 chroma will show red text rather blurry. Then there's input lag, which I've not been able to find any tests of on that one or it's current model. Panasonic and LG are the two brands lowest in input lag though, LG more so last year (depending on model), Panasonic more so this year.
Make sure you look at one in store if you can, better yet with a game console if you can to get an idea of the lag. Amazon has the current 42CS570 model that adds revised (Triple XR vs XR) video processing and SIMPLINK for $30 less. You can even get it as low as $470 on Amazon if you have approved credit and sign up for their Visa Rewards card.
http://www.amazon.com/dp/B006ZH0JQM/?tag=tec06d-20
Note that significant changes in video processing CAN raise input lag. My Panny TC-L32U3 has been tested to about 23ms lag. I play a wide variety of games on it without any noticeable lag. The model you're looking at may be slightly better when it comes to blur though.
So it can be a tough call in weighing in how much you care about movies vs games. If it's mostly for movies, you may want the better video processing. If it's mostly for games, and esp if you play competitive online shooter, race or fighter games, you may want to opt for the lowest input lag.
I looked at last year's and this year's LGs and Pannys before deciding. I knew I wanted a good quality IPS panel. With Panny that is easy because all of their TC-L models have very good Alpha IPS panels. With LG they'll actually put you through a panel lottery so you don't know whether it will come with an IPS or VGA panel. LG's models (esp last year's) also seem to be pretty inconsistent on input lag.
Note that Panasonic's closest competitor to the 42" LG 120Hz TV is already sold out most places, and Newegg doesn't even carry them. The TC-L42U30 is a pretty good set though. This is not a very good time of year to buy really. Both prices and selection aren't very good. I bought mine a week before the Superbowl for $350 at Amazon and they credited me the difference in price when it dropped to $330 a week later.