I made this tonight. Its awesome, even though my tiny grocery store only sells regular old green jalapenos. I'd like to try it with a mix of several peppers mixed together, say, serrano, jalopeno, red chilis, habanero. I think that would make it the best.
I think it was a bit sweeter than the store bought variety. The recipe calls for a cup of sugar. Next time, in addition to changing up the pepper content, I will probably use 1/2 cup sugar and 1/4 cup brown sugar (or possibly some combination of sugar and honey). I think cutting the sweetness and adding a little different type of sweetness might be good.
Update: I made a new batch today with the following. Instead of 1.5 lbs jalapenos, I used 1lb cherry hot peppers, 0.5 lb Thai red chilis and 2 habaneros. Also, no white sugar, and only 1/3 c brown sugar. Put 1/4 c salt, because I thought the first iteration was not salty enough. This batch is fucking amazing, and I think I like it more than store bought sriracha. Its maybe a touch salty. I think that I might have thought the first batch wasn't salty enough, because the overpowering sweetness killed everything else. Its mostly perfect, however, and I would highly recommend.
Three things: 1. I needed to cook it for a half hour or maybe a little more to get it reduced enough. 2. when you bring it to a boil, watch it like a hawk, then reduce to simmer right away. Otherwise, you'll have a giant pepper puree mess all over your stove. It boils over pretty easily. 3. I didn't take the seeds out, becuase i like a little more spice. Didn't ruin the texture at all.