I use the Google Apps/Gmail interface also. I've found that as it has matured over time there are less reasons I would want a desktop client and more reasons for having the portability of a cross platform, location independent web interface.
I use IMAP on gmail with opera. I need a desktop client, for times when i'm not connected and quickly need to search an old email for some small little detail.
I just use it as an offline backup, and keep it synced.
Me too - using Gmail + Gears w/ Safari 4 Fluid app, and a dock badge 'inbox count' userscript. Google will tell you you can't install gears with safari 4 - but it works.
It is available for Firefox 3.5 and it does sync all your recent mail, including attachments. It uses an automatic, non-configurable heuristic to determine how much mail to sync. I believe mine syncs the past 1 year's.
Gmail is a class act when it comes to web apps.