cname vs a record?

[test1]

Currently on my site, users get their own personal site that they can point a custom domain to. Right now they point their domain to their site by setting the a-record to our server's IP. I've recently been doing some research and it appears that using a cname would be better because it points to a domain instead of an ip address so that if I ever wanted to move hosting I could without messing everything up. I use mod rewrite to actually grab the custom domain and direct the browser to the users site, should this work with a cname also? If so do I have them delete the a-record and add a cname record or how would that work? Also any suggestions if it does work on how to migrate old users using the a-record to the new cname structure? I'm guessing this would be a manual process but it would be great if their was some sort of workaround.

[test1]

After doing some more research it looks like CNAMES won't work because I can't point the base name using a CNAME. Is this correct? Meaning if someone enters "www" first then the CNAME works, but if they just enter the domain it wont'? If this is correct does anyone have any suggestions for making where the a record points to more "dynamic" so I can go in and change hosting on my end and everyone else don't have to change their records again?

[phranque]

wildcard cname?

[Robert Charlton]

Here's a thread with some background on CNAMES that might be helpful, even though it doesn't answer your question directly. I suggest you read the whole thing, as there's a misstatement in an early post that gets corrected later....

www and non-www : cname redirection
How to actually set up the cname record
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