My boys LOVE this program. Minimal violence, no bad language, funny happenings. If your kids love aliens, etc. This is it. Some younger kids might find the aliens a bit scary but I doubt it. My wife and I enjoy it also (a bunch more than other animation such as Fairy Odd Parents which we refuse to allow on the TV).
I am really impressed with the different plots also. Actually kind of nice to see something that is not a rehash of the 10,000 Scooby Do episodes out there. If you TiVo or DVR episodes, watch out for the marathons which will fill your recording space up in a flash.
Also check out the Martin Mystery web site: MartinMystery.com for some fun things for the future alien agents to do!! The programming has some holes but is it is quite functional and fun.