In terms of speed I'm sure it is fast enough. However, if you want to do anything more than host a few static pages and files I think you will find it lacks the features necessary for a fully fledged website. For example, I don't think they offer DNS services or database options. My recommendation would be to look at
TJR Networks or
Myacen. Both are good hosting providers with good prices. If you need 24/7 support go with the later, if a small time delay doesn't bother you, then save your money and go with the former.
I personally would never use .Mac to host a website.