" Super duper memory hog - this comes from keeping every single page you've visited in memory... at all times. After an hour or two of browsing this is like having 80+ tabs open in Mozilla. "
That's not quite right. iRider utilizes available memory to cache pages, but will purge them to accomodate other applications or other pages. Mozilla doesn't do this -- open lots of tabs and it'll thrash.
http://www.irider.com/help/ToolsMenu.htm#MemoryTab
" IE rendering engine (the Mozilla Gecko engine renders pages much better than IE does often, and supports more advanced CSS features) "
IE does seem to be falling behind the latest standards, but I think "much better" is a stretch. It's extremely rare to run into problem sites with IE/iRider, for the very reason that IE is so common (for better or for worse

).
" However, there are two features that are really lacking. One is the a standard Favorites menu. Instead you have to open a favorites page and navigate it by clicking thought it (assuming you have your favorites organized into a hierarchy) in which each favorite folder corresponds to an entry on the sidebar. "
Compare the two. In other browsers with a menu:
-- Click the Favorites menu. (In IE this'll be a single column with its silly scrolling feature)
-- Click intermediate folders if necessary
-- Click an item to open a page
(Then do the above again if you want to open more than one.)
With iRider:
-- Click the Favorites icon, or the item in the page list (which can be a subfolder), or press F8
-- Click intermediate folders if necessary
-- Click an item (and possibly more than one with Surf-Ahead or opening selected bookmarks)
Granted, there's more mouse motion, but the number of steps is the same, isn't it? And there are mitigating advantages. When you're on a page (perhaps a page you want to remove from Favorites), click Parent (F9) and you're on the Favorites folder where it came from.
" It just doesn't seem right to pay $30 for a browser... "
Yeah, I mean after all, there are some games that cost that much!

I've been granted permission to say that sales are brisk.
" MyIE2 and AvantBrowser are both excellent MDI/tabbed browsers "
If tabs do the job for you, then there are freebies out there. We believe iRider is qualitatively different: a visual map of pages, organized by site, that you can riffle through, opening multiple links/bookmarks at once in various ways, bookmarking multiple pages, etc.
Dave
Wymea Bay - iRider