Yes, the joysticks they use on some Sony phones can jam up. I think it's just dirt build up though so you can clean them out. The mad thing is that they use the same chassis underneath but fit different controls to different phones. The W810i and K750i are near identical under the skin but the joysticks and buttons are different. The K750i is actually better value as the music player, camera etc are just as good as the ones on the W800i, just that poorer headphones are supplied and the software is different. The W800i joystick doesn't seem to jam up though, it's a one-piece pad.
You need to really compare the Sony phones to Nokia ones at the price to grasp the difference. The Nokia 6300 is a phone with a poor afterthought camera stuck on. The Sony K800i is a digital camera with a decent phone built in! Even the W810i/K750i has a flash and other features that make picture quality a lot better. You can even use the flash as a torch or set it to flash S.O.S. !
The daft charging/headphone connector block on the Sony phones is a pain though, I don't know why they did that. You can get an adapter but it still seems obtuse.