I've been playing with SVCD (mpeg2) encoding in OSX for a number of months and have found nothing that provides an accetable result (unless you are willing to let your Mac grind away for 10-12 hours while encoding takes place).
A reasonable alternative is a product called "Instant DVD" from ADS Technology which you can find at TigerDirect for about $90. Pick up a USB-equipped PC (PIII/466 or better with a sound card or motherboard sound I/O) for under $200, plug in the unit, and send analog A/V through the unit into the PC. The package does real-time encoding so a one hour movie is encoded in one hour. I send my finished iMovie back out to the camcorder via FireWire, and then connect the analog ports on the camcorder to the Instant DVD unit. Works like a charm and you can encode as VCD, SVCD, and three different bitrates for DVD. The mpeg1 and mpeg2 files are cross-platform compatible (with QuckTime mpeg2 Decoder or VLC); I fileshare and send the captured movies to my Mac where VCD Builder can make SVCD tracks that Toast will burn. (You can also use Nero Burning ROM on the PC but that's not included with the package. Nero works great and even has an SVCD plugin.)
Don't confuse this product with ADS Tech's "Instant DVD for Mac" product (at about $280). That package will not produce anything that can be burned to SVCD. The encoder chip and software produce proprietary format mpegs that can't be processed by VCD Builder nor Toast. In fact, the files arrive on the Mac (through the encoder box and software) in a format that is "overstuffed" (too high a bitrate) for use in anything other than the included software (which transcodes the movies into VCD and DVD).
Drop me an eMail if you have ?'s.
Barry