Unusually, as well as the OS X version, iCab's developers continue to support OS 9, which makes it an ideal option if you want tabs and other advances on an older machine. It's also a tiny download, and so is suitable for those on dial-up who might struggle with Firefox.
Despite its svelte size, iCab does have some interesting features, including a very handy Kiosk mode that can be used to exclude browsers from other parts of the computer. This would be useful for keeping the children away from other programs during browsing sessions, or for those who allow public access to their Macs; quitting Kiosk mode requires a password.
There's also a nice Standard Links toolbar that combs through each site you visit and then presents links to, for example, the homepage, a site map, copyright information and any mailto: links.
A small icon between the address and search bar will indicate whether there are errors on the page; this would make it a good choice for those who occasionally build web pages. This tool can be easily removed, though, using the very comprehensive Preferences.
iCab seems a little bit niche for the average user. The interface is simple enough for daily use, but it's easy to become bogged down in the Preferences dialog that is almost as complex as OS X's. But the standard version is free if you want to give it a whirl and the professional version costs $29.
Like Shiira, iCab is happy spoofing Internet Explorer 6 on Windows XP and so had no problem accessing otherwise restricted banking sites.
iCab is an excellent browser for power users, but those looking for similar tools with a more intuitive interface should check out Shiira.