I use HSI on my rig, and I like it. Time from call for flame to flame is about 1 minute with my modules. It goes through a prepurge and then ignitor warm-up sequence before it opens the valve. The amount of heat lost in said minute is pretty negligible in my opinion, and I like the idea of flame rectification.
The modules I use are honeywell s8910u. They are really pretty simple, you supply 24v and 120v to the module, and it then sends 24v to the valve and 120v to the igniter upon call for heat. The modules are available on ebay for 50 bucks or so. I will take some pictures of the modules, valves and ignitors tomorrow if you are interested (my stand is still in progress in my shop at work, but wet tests have proven the hsi to be satisfactory)