I have a W910i and it's not the best handset I've bought, I've only had it since September 2008. My last was a Samsung D900i, and that sadly died (I'd only had it a year!).
All of my past few phones have been useless, the W910i battery dies every 48 hours, as did my D900i's (and toward the end of its days, the battery would last 12 hours max!).
I also used to have a Sharp GX15, basic, but super battery life, and had all the necessary features of calling and texting etc. I still have it somewhere... the battery dies really quickly, although the phone itself is still in supreme condition, I am tempted to revert back to it, if I can buy a cheap-ish new battery for it. Although I am no longer with Vodafone (won't take any other network SIM cards, I've tried!) and the SIM is locked since I haven't used it for a few years.
It really does waste my money, these Sony Ericssons and Samsung's. The W910i is better than the D900i in terms of software, but in terms of look, the D900i wins.
I've spent far too much on phones these past couple of years, and it's because they're just rubbish and pack up on me, otherwise I'd expect a good mobile to last at least 3 - 4 years.