I made the transition to Google Apps and browser based email/calendar about 2 years ago. It was pretty difficult to ween myself off of Microsoft Outlook and Exchange which I’d been using for 10+ years. In general I was happy with GMail and, in many ways, I think the Google Calendar user experience is BETTER than any fat client solution I’ve seen.
I even went to the trouble of consolidating several GMail and Google Apps accounts using forwarding and aliases. It all was working pretty well. Until I hit the 4th email account where I needed to keep things separated. I was spending all my time switching from one browser window to the next checking multiple inboxes the hard way.
Then it happened. I’ve moved back to a fat email client to manage all these accounts. Apple Mail, the free client included in $29 OS X, is fantastic. It manages multiple accounts gracefully and the default configuration works great with Google Apps. Don’t try to outsmart it. Just take the defaults and be happy.
One subtle trick is knowing that you can use multiple email addresses in a single account in Mac Mail by separating them with commas. That was the final piece to make it all work perfectly for me. Note that you need to setup these secondary aliases in Gmail as well. Read here for more details.