Thanks for the constructive criticism. I didn't notice the upgrade bugs and I've fixed them for the next version. I'll continue to tweak the difficulty of it as I can, but I do realize that siege tanks are too powerful as it stands.
I spent a little time to create a map that I though might be simple and fun, if not a little fast paced. You try to defend the Shrine on the right hand side as zerg come at you. You can build units in the factories, and upgrade them in the shrine. The zerg get progressively harder, and I am working on finding a good rate of increase for the difficulty.
I hope you enjoy this map and leave some constructive criticism. Thanks.