Useful tip from here: Safari version 1.3 and above includes a Javascript debugging console, the absence of which was a major hassle. Web development's still not as fun as with Firefox, but this helps. The console's not accessible by default, you have to turn on a menu of debugging option. Do so with this command in a terminal while Safari's not running:
defaults write com.apple.Safari IncludeDebugMenu 1
Set it to 0 to turn the menu off. There's a lot of interesting sounding stuff in that menu, but I haven't played with anything else yet.