CF Reader with Multiple Slots?
The Delkin ImageRouter is the only one I'm aware of other than the Sonnet Dual ExpressCard reader: http://www.sonnettech.com/product/produalcfadapterexpress34.html
The ImageRouter was convenient in that you could put four cards in at once, and as long as your ingest software could handle it you could fire off a concurrent/sequential downloads. However, depending on your cards the aggregate performance would probably top out somewhere between 16 and 25 MB/s. Rob Galbraith's site has some commentary about it at http://www.robgalbraith.com/bins/reader_report_multi_page.asp?cid=6007-9392
When I'm on busy jobs and downloading lots of stuff (sometimes 40 GB/day, on mostly 16 and 8 GB cards) I've been happy with either one or two Lexar USB readers. Even the current SanDisk Ultra cards will get close to 30 MB/s each in these. With concurrent ingests my laptop maxes out at about 50-60 MB/s.
If you travel, another advantage of two Lexar dual-slot USB readers (the "dual" referring to the CF + SDHC slots) is that even together they're MUCH smaller/lighter than the ImageRouter.
I wrote up some notes about this at: http://blog.davidburren.com/2011/01/memory-card-readers-pros-and-cons.html