Hi Nathan
I will give you feedback about @mail as it comes, here's a few thoughts:
I don't know about you but I use Ensim pro 3.7 on my server. You may know that squirrelmail is preinstalled on ensim, so why am I going for @mail? Well, you are right its expensive, as compared to squirrelmail which is open source. SQmail is liked by coders who dislike bloat and want a simple html interface, fair do's but my clients are a fussy sort who are used to the likes of Yahoo and hotmail etc. I don't mind SQMail but I have had several complaints about it's amateur looks etc. so I decided to spend some cash to make my clients happy (hopefully

)
I researched a lot before making this decision and the only other two webmail alternatives that I felt were contenders were Horde and Hivemail.
Horde is again open source and tempting just for that, but somebody needs to give thier site a makeover because at first glance it just doesn't seem clear what Horde is! there are about 6-8 different apps which are part of the Horde email package (I'm being a bit vague probably) and the learning curve just didn't seem worth it to me. ( I have other things I need to concentrate on, know what I mean)
Hivemail seems pretty good, a nice looking package but the pricing seems more suited to installing it on your own site, not for a reseller like me.
@mail only requires one install and all my clients can use it, you get the source code so its pretty customizable. You can create a separate login page, branded how you like for each of your sites..........
So thats why I decided to take the plunge with @mail. Who knows, I have bitten the bullet with many a promising piece of software before, only to discover that it doesn't do what it says on the tin Or worse, the support is nonexistent.
So far I have only installed the demo version which I got up and running on my Powerbook in no time, the installation script is nice, minimum effort, the way I like it :-)
So I'll keep you posted once its installed on my linux box if you like?
now back to my other problems........
cheers
Peter
ps I forgot, having just one install vs multiple is great too (for obvious reasons)