I've been using gmail almost exclusively for about 4 years now - I find the convenience of webmail essential as I work at lots of different machines, and it doesn't make sense to set up desktop email on all of them. One thing I do miss about not using a desktop mail client is the integration with my address book and photo library, and the ability to drag and drop files, but I have so much mail in my account (I subscribe to a few high volume mailing lists, and never do any tidying), that most mail apps choke on the volume of mail they need to download. I mentioned this on twitter, and someone pointed out mailplane - a gui app that loads the normal gmail interface, but adds on integration with addressbook and iphoto, amongst other things. It's not free, but i'm a couple of days into the 30 day evaluation and finding it very useful so far, so will probably buy it ($25).