Yup, it's good fun, Freight Dogs is good too (that's kind of like the 'bush pilot' version of it with less of the empire-building, but I'm not sure if Freight Dogs supports FSX). Cargo Pilot definitely is patched for FSX and Vista too (although it doesn't like 64 bit apparently).
CP's airline equivalent - Airline Pilot (not FSX compatible) - and similar utilities, or even joining a VA tend to give FS a bit more purpose, as does doing it all properly with the add-on airliners with all the systems modelled correctly and the FS2Crew add-ons (which are really very cool), so most things like that are worth a look, but be sure to check for FSX compatibility (or planned patches, or get a cheap copy of FS9).
Note that Just Flight is (
http://www.justflight.com/) currently working on Cargo Pilot 2, which is going to add more functionality and flexibility, which means you can probably get the original CP cheap, or, you might wanna hang on a bit, check their forums and see how far off CP2 is from release, not sure how far along they are with the second version though, so maybe it's worth getting the original anyway. Or, why not try out the demo?
If you want to get really serious, this is worth a look too:
http://www.aerosoft.com/cgi-local/re...i?showd,,10450
As it emulates real world operations very closely, but that said, stuff like Cargo Pilot is probably more fun!
Chock