For a while I have been using Gmail to manage my "alternate" email address. That is... the one I use to sign up for crap, accounts, etc. My main account I host on my server and retrieve with the Mail application on my Mac. Unfortunately, I can't access my mail server from Blue Sky due to firewall and security issues (not uncommon), so I have been getting my personal mail for a long time using Horde's IMP webmail application.
I have come to realize however, that I enjoy checking my junk mail through Gmail more than my personal mail through IMP. And recently I found myself composing personal emails though Gmail rather than my IMP installation. IMP has become too slow and clunky compared to Gmail's mostly reliable, fast, and slick interface. My main gripe is the fact I have to open a new window every time I want to compose a new message. But Gmail has a lot of other easy time savers too (like address auto-completion, and of course the endless archiving).
I spent some time fooling around with Roundcube which provided an encouraging alternative with clean interface, drag-and-drop, and just a nicer user experience. But ultimately, it was too buggy, and still disappointed me. I had problems with messages caching and then disappearing (!) and found myself often unsure of where my mail was and in what state. Granted, it was an early beta release. I think they have a good potential when they get to a solid release but... I'm impatient.
So now, I am bouncing my personal email to a new Gmail account. I can manage my email on my server and on Gmail, assured that wherever I am, I'll have quick and easy access to my mail. The only challenge is staying logged in to both accounts at the same time, so for now I'm using the Gmail Manager Firefox extension to manage both of my accounts. We'll see how it goes for the next week or two.
There is another option for people to manage 2 Gmail accounts in the IE Tab Firefox Extension, but I'm on a Mac and otherwise hate IE anyway so that one isn't really an option. I may end up forwarding email from 1 Gmail account to the other and use filters to sort them, but then we're getting a little ridiulous aren't we? I'm open to ideas if anyone has them.