Very fun, but very short. Despite having 30 possible levels, you do 10 per run-thru each time...so you could finish the whole game in a little over three hours if you worked at it. Wicked fun while it lasts, Aces of the Galaxy is unfortunately hampered by similar problems to what too many of Activision's other older titles on here have - namely poor maximum resolution [1280x1024 standard / 1280x720 wide], no saving between levels, and spotty at best controller support. It controls very well with a keyboard and mouse though, and gets nice and insane near the end. If it can be snagged for $7.50 or less, I'd say it's worth it if you like more casual space schmups, and it also happens to run very well on newer machines - something way too many of the other old Activision titles sadly can't boast.
Best part: You can kill the credits on game end, including government agencies. Not that I'm advocating doing that for real, or anything. ;P