I was surprised I didn't find much info on a search on this site. Anyways, I have been playing Steam Hearts the past week. Most of what I heard is that it is just a decent shooter with bad Hentai pervert stuff in the cutscenes. I love shooters and thought this expensive title would be a good one to play on my Christmas break.
I think the game is great. There is a ton of action, basically nonstop. The game has a good length and the action is fun all the way through (No long dead zones of mindless blasting ala Blazing Lazers or Spriggan). The game is also fairly difficult to beat, especially with one credit since you only have 1 life so you will be playing and doing a fair amount of memorization plus some good reflexes to conquer it. The last Boss and stage 4 Boss are particularly tough. The graphics are also pretty good, nothing spectacular but the Bosses are nice and the colors are easy on the eyes even when there isn't a ton of detail. I also think the soundtrack is great, especially the techno sounding tracks on stages 3 and 5.
Good graphics, great sound, tons of action and a nice challenge. What else do you need in a old school shooter? For me there are still some better shooters on the Engine but this one is in my top 10.