There are plenty of tools for doing web development. Most of them are very stable.
Check out Interarchy (FTP client), Textwrangler (http://www.barebones.com/products/textwrangler/textwrangleradmin.shtml) (free, includes a FTP client) and, of course, Dreamweaver MX.
On a standard Mac OS X install, you'll find Apache, PHP, MySQL, Java and a shell terminal (useful for installing apps and configure your VPS).
If you wish to do audio editing, Flash development or video editing, you'll find the tools you need. Check out also www.macworld.com.
Consider this: any portable Mac can do desktop spanning (dual monitor). iBooks will need a patch for that. That's very useful when developing websites.
As for browsers, you'll be able to test your pages on Safari and Firefox but you'll need a PC (or Virtual PC) to test your pages with Explorer 5/6 Win.
Hope this is of help to you.
Corrado