Thanks for all the help - I was looking for the Logic private midi issue myself and was about to pose the same question! It seems there is a fair amount of 'Spark bashing' going on - which i think is very unfair. There will always be some issues with any new product or software. I myself had a problem with not locating audio samples on an external hard drive - once spark was installed and run. You need to be VERY specific with folder the samples are located in and not just the hard drive icon or sub folders. (and there are a lot of sub folders!). Otherwise it has been stable and fine (I am on a mac - I don't know if this is more stable than windows)? - certainly the guy in the shop demo-ing it - was having lots of issues with delay and non triggering with his windows version? But I kept the faith and bought it anyway!!!
For what its worth - I think the product is excellent and I am enjoying learning the more 'hands on' drum experience! Keep up the good work:)