Looking to upgrade

So, my current phone is an old Galaxy S 4G from T-mobile, I can't upgrade my phone for about another six months, but honestly, gingerbread has failed me dearly, and the phone is so laggy I can hardly use it at times, so seeing as I can't upgrade, what are some good, newer unlocked phones, Obviously, I'm looking at the Nexus 4, but I was wondering about some other opinions, please and thanks