My brother has an X5. Gameplay is great, although I wish there were more diversity to them. Lag is not a problem unless you use up too much memory. Apps are almost the same as a typical i-Phone, and the app store looks simple, though I never used it myself.
I don't know much, but I could ask my brother more?
i have a sony ericsson xperia x10, and when i have alot of apps runing, my phone lags.
if this phone is an android phone, i suggest you download an app killer, this app force closes the apps you wish it to close.