Len,
Tobacco float tray systems are used now around here in place of cold frames to start tobacco seedlings. Rather than sowing direct in the ground, you sow into these styrofoam plug trays, which are then set into plastic lined troughs filled with water. You can control the amount of water the tobacco seedlings receive because it takes the water up from the trough, rather than from rain or overhead watering. And when it comes time to pull plants, it's much easier to pop an entire tray out of the trough, rather than to bend over and pull plants out of a cold frame
It's very similar to those Bio-domes you can purchase with the sponges. Instead of using the sponges, you use soiless mix in the tray, and press dibbles into each plug area using a nifty dibbler that does the entire tray at once. Watering the trough, rather than overhead on the plants, helps lower the risk for disease. Float trays are about 13"x26", with anywhere from 48-200ish cells per tray. The ones I have access to have 96 plugs per tray.
I don't grow too many tomato plants ( 50 or so), but I do start lots of perennials from seed. I think I'll take your advice and use the float tray for my perennials and stick to my old tried and true method for my tomatoes. If this works well for my perennials, I will purchase new float trays next year and try my tomatoes in them. And just to be on the safe side, I will make sure the tomatoes are on the furthest end of my light table from my float tray.