Nice phone, I've been using mine for almost a year now, and have been largely happy with it. Some grumbles though:
1. Camera - utter rubbish, I had a Sony Ericsson k800i before this, which broke and I had to replace it, but the camera and flash were 100 times better. Any sort of movement from either your subject or you means a blurry photo, even in broad daylight. It's almost impossible for me to take photos of my children on it. In saying that, I don't really use it that often to bother much about it.
2. You can customise ringtones, but only have limited options for changing messaging tones, which is pretty lame (I like my phone to Moo! when I get a text message!)
3. Again, it's a lot more difficult to make your own wallpapers for the phone, because it doesn't display them correctly. There's not an option to full screen a wallpaper. Every phone I've had has had this option, so it's a bit of step back. You can do this with photos you take on the phone though.
4. Texting is easy enough, but a bit fiddly. I don't do text speak, and when I spell don't, I spell it as don't, not dont, and it's a pain getting the ' symbol, as you can only get it through the special characters menu. All other phones I've had have the ' character on the 1 key.
5. Sound quality of music through headphones (included or otherwise) is muffled.
6. If, like me, you use a bluetooth headset, there's no voice dialling, which defeats the purpose of using a handsfree kit. An old Nokia I had 10 years ago had this, so what's the deal? You can answer calls through the button on the headset though.
Minor points, except for the very poor camera, which the phones looks and size more than make up for. Having used the phone for nearly a year, I can confirm that the build quality is just fine, and slider on my phone is still nice and smooth.
I would recommend one, and you can pick them up new and unlocked on eBay for around £50 now I think.