speficic to your quesiton about UMTS or not.
I live in Chile where no Carrier supports UMTS basebands 900/1700/2100 - I can live with 2.5G it is enough to get by.

I have never regretted buying it webbrowser and chat support is awesome. if you are a medium 2 heavy user you will have to recharge during the day though as it does not last for the day if you use it for IM and Web.

Integrated SIP calling is also awesome - applications are a little scarse but will increase with the QT push of Symbian and the launch of N8 - so I hope & guess.