This o2 service has been available in Germany for quite a while - I've been thinking about this, too (my main mobile operator is o2 anyways). But, then, I heard from some people - one beeing my direct neighbor - that the "home broadband part" wasn't all too good in terms of stability and transfer rates. So, I will observe this a bit longer...
Wow! Unfortunately, I must agree with most of this. Even alot of "positive thinking" doesn't really help. i like "Class-F" - I call that AB (advanced bullshit) at times...