Sony Ericsson S710a

ive been reading about people saying that their fone is laggy and other people say that its because of the firmware and the new fones dont do it. ive even read how to find the firmware version. my questions are which is the new firmware and how laggy are we talking about? on my fone, whenever i press a button, it take between 1 and 2 seconds to react... is that what everyone is talking about? or does theirs lag more? it seems like alot to me, my last phone was a motorola v400 and it at least seemed like if i pressed a button it almost immediatley switched screens. any help?