Gmail is very nice and the search is great and all, but I do a lot of filtering on my mail, and not being able to use something like procmail to make unlimited rules and move things into as many folders (or “tags”) as I want is annoying. Tagging vs. folders means you should be able to apply more than one, but with Gmail you’re not, and the rules interface is very crippled. What it comes down to is, Gmail is great for most people but if you’re more technologically sophisticated and want complete control over your email, stick with standard tools.