I got my Xperia Play on launch day and I remember it cost around £500, so I opted for a 2 year plan instead. Now it's extremely cheap and it's totally worth it.
I use it at the very least an hour a day for gaming. You can pretty much download any nes/gba/gbc/megadrive etc game and use a good emulator (I think it's legal as long as you have a copy of the game). I can't describe how awesome it is to play pokemon on the go, for like a minute or so waiting in a queue. I keep hearing childen telling their parents "look! he's playing pokemon". Though I still own an nes, I would never bother playing Super Mario Bros 3, but it's so much easier on xperia and the controls are really great.
I've tried a couple of games developed specifically for xperia, but it's not that fun to play them on the go. Backstab, Sacred, Spiderman and a few other are great, but I'd still much rather play Mario when waiting for the bus. One could argue that I could simply buy a ds/gba, but I don't like carrying any other devices apart from my phone.
So in my opinion, since you're a gamer you should give it a try (especially if a friend own it and has emulators installed) and then decide.
