Casual Survey: mobile telephony / data providers in Germany

Which mobile provider do you use here in Germany? What do you like/dislike about them? Think about coverage. Billing. Pre-paid vs. contract. Perks. Roaming (EU and beyond). Especially welcome are your comparisons between operators/plans.

I’ll start:
I’ve used Debitel pre-paid for phone service. O2 for pre-paid data services in Germany. Vodafone and Telekom for business and personal telephony and data plans.

Seems like they all are the pits on the DB stretch between Regensburg and Nuremberg. Vodafone and Telekom are just okay for coverage in our apartment. O2 doesn’t work at all there — good thing we don’t need them to and didn’t move there with O2 contracts in place. But I like their pre-paid surfstick plan (with which I use a mifi instead of their stick and am publishing this now).

So, your turn now.