I've been with Vodafone for about 8 years. Mainly cause I liked the phones available to the GSM network. I've always been prepay up until mid 2008, when I went on contract. I get what I need and don't have any problems, Although I'm not really what you'd call an 'intricate' user. I text, make a few calls and browse the net etc.
I don't really see a need to move to Telecom. I'm happy where I am.