Don't know about their servers, but I would never buy domain names from them again.
I bought one which I wanted for a reseller, and wanted to use ns1 and ns2.resellerdomain.com as their nameservers, pointing to one of my servers.
The 1and1 control panel doesn't give you this option, only the option to use ns1&ns2.someotherdomain.com, or 1and1's own nameservers.

Everytime I asked them about this, they did one of:
- Tell me how to point to someotherdomain.com
- Tell me I needed to create a subdomain and, when I told them I couldn't do that (not that it helps anyway)
- Tell me I cannot create subdomains on a name only package, that I needed to upgrade to a hosting package, despite me saying I was trying to point the domain to ANOTHER server

Variations on this happened 3 or 4 times, going round and round in a loop for a couple of weeks. I then lost the will to live and gave up, taking my business elsewhere.,,,