Here's my friend Amnon with his M1009:
Problems I've seen on these are:
Missing bracket on the starter. Techs think they're redundant and leave them off when servicing the vehicle. What the bracket does is keep the racket from the Diesel from shaking the starter and cracking the starter mount.
Crappy glow system. There are retrofit kits to upgrade them or just rig a momentary switch in the cab to activate manually.
There is also some electronic component that overheats regularly but I can't remember the name. I've seen kits to re-locate the part to cooler areas under the hood.
Most military vehicles fall into the catagory of "barely adequate" in terms of road performance but since the M1009 is derived from a civilian vehicle, it rides and performs somewhat better than most others. However, the engine is loud as hell (relative to my F250) and you might end up having to wear hearing protection for extended trips.
You can email Amnon above. He's a nice guy and will answer your questions. I can give you his email via PM is you want to persue it further.