Well we used to use 1&1 on RcKingdom, was fine for a few years. Certainly not the cheapest for the site owner to pay, but the backend was easy enough and hosting was reliable. However when things go wrong expect the worlds worst customer service. I won't go into specifics of our problems there, but basically after weeks of downtime the site owner got annoyed and I migrated to Primehosting.
However I also setup Nitro Models on 1&1 and that's been okay. No problems as such, so we have not had to deal with customer services. This was a shared server setting which was hit and miss with speed. The database are not local on the server though, and I found they overload some of their database serves. After creating several databases, it automatically selects a random db server, and using trial and error, I found the fastest one and that seems okay.
At NeoBuggy, which due to the massive popularity of the website, we're current using 3 dedicated servers, at 1&1 also. These have been fine. Not the cheapest, but not the most expensive either. They deal with the massive load fine and all is good on that front, when Phil says Neo is largest 8th news site he really isn't kidding!
I know also Jimmy is 1&1 dedi as well now, and well I've personally noticed the site has been running smoothly recently. Hopefully he'll post his views on it.
Basically there are LOADS of hosts out there, I know as I manage sites on loads of different ones. All I can say is, I haven't found the perfect one yet. If anyone knows the perfect host, I would really love to know. 1&1 have awful, awful, awful customer service but apart from that the actual hosting service really is quite okay.
If you are looking for good shared hosting, I certainly would check out Prime (
http://www.primehosting.co.uk) also. I setup DXR's site on Prime (
http://www.dirtxracing.co.uk/home.php) and also migrated RcKingdon to it as well. I can't comment on their dedicated servers though, having never used one from there.