I'm brand new to this site, so my info is probably too late for 2012, but perhaps useful for future years.
I started Cobaea scandens 'Alba' seeds (purchased from HPS - 100 seeds/pkt, cheapest I found) on Feb 12, 2012. 2 unsoaked seeds in each 1-1/2"x2-1/2" 6-pack cell = 12, planted on edge just below soil surface. I also soaked 12 seeds overnight and planted them on Feb 13, 2012 in the same way as unsoaked. Both were under lights and inside sealed poly produce bags but not on heat mats. Both began germination on 02/20/12 and completed on 02/22/12 with 100% germination. For these, it appears that soaking only made a day difference (not enough to deal with that slimy seed coat soaking gives). Poly bags removed after germination completed of course.
BTW I've tried these before from other seed sources w/ MUCH poorer germination - it seems that seed source makes a big difference for these plants.
After thinning to 1 per cell, I potted them up on 03/12/12 (actually could have been at least a week earlier) in 4-1/2" sq pots that were 5" deep. They remained in those pots outside (brought in if nights cool) in full sun until our plant sale on 4/14/12 - bamboo staked up, fairly root bound and about 3' tall. Kept one "runt" for myself as a test (they're uncommon here - don't know if they're a cool season plant or if they can handle our heat and humidity) but the plant established very quickly after transplanting even being quite rootbound.
I'd love to know if anyone in the Deep South (hot, steamy) has had success with these.