I have a Sony Ericsson and will probably never purchase one again. Maybe I got a lemon or something but I'm definitely not too pleased with its battery life, its performance etc. Before you buy ANY phone, make sure that it has every feature that you may want. For example I just learned a month or two ago that my Sony Ericsson doesn't even allow for call forwarding whatsoever. It's apparently not a feature that's built in so I'm screwed because I need it for work. So if there's features that are important to you, make sure the phone you want has them.
