1&1 was the first company I was ever forced to use telephone support for, after they failed to answer e-mail support tickets. They suggest waiting for 48 hours for a reply, but are sometimes unanswered regardless. (Note: latest support requests for a client were answered - 1 week later.)
Additionally, you may find the support technician knows even less about websites than you, let alone anything about hosting and server issues. I have certainly been in that situation in administrating a client account with 1&1.
Their servers aren’t particularly reliable either, with real processing speed problems coming up, either because their hardware is old, or because the servers are over-populated.
An additional point of consideration, though, is that you may find your website being hosted in Germany. This may be a real concern on Top Level Domains, because if hosted in Germany, they may not show up on UK only searchs of
Google.co.uk, even though you are hosting with the UK arm of the company.