I mainly want to switch because I'd prefer to have all of my contacts sync via iCloud (all the fields and so on are then consistent across devices). But without the e-mail portion too, it doesn't make sense because I use webmail interface (Gmail or iCloud) from my work computer.
On my home computer, I would prefer to have my Mac Mail set so when I send an e-mail, it comes from my custom email name (different domain suffix). I cannot figure it out with iCloud. Using Gmail, it's not a problem. It's just an e-mail forward address and I can direct mails that come to it to go to either or both Gmail and/or iCloud mail. But I'd prefer that when I send an e-mail, those on the other end see the custom address as well.
Here's the help I followed:
http://support.apple.com/kb/HT4864