I separate everything to avoid all in one basket. i.e. domain registration, email, website hosting or shopping cart.
Yes, you have to pay for all of them or get them provided by your web hoster but I just feel that someone offering everything is promising too much. Well, that’s my opinion anyway.
Domain registrar – iwantmyname (domain name specialist nothing more – very easy to deal with and they hide your identity like your full address)
Email – thexyz webmail (webmail only and you can custom whatever web address you want very easy. I just informed my domain registrar to point to Thexyz webmail)
Website hosting – Virb (yet to decide but I like the nice simple templates and the price is reasonable for me).
Shopping cart – yet to decide.
I can migrate etc all the above anytime I want to retain flexibility if I want to change in future.