I've been playing it a lot lately too... Last night i got the high score acheivement, couldn't beleive it.
I talked to a pro who got the 100 wave achievement, he gave some good tips. Just search youtube for robotron for some wave 100 strategies.
I still can't beat wave 9 though. The main strategy is ALWAYS go for the family, they are top priority. What you want to do is get at LEAST 1 life each wave (starting with wave 8 or whatever).
Joust is friggen hard too.