These trucks are tanks, they are incredibly reliable more than almost any other truck I have ever owned. These trucks have proven themselves so valuable that we switched our entire fleet to them from the Ford, Fuso, UD, IH's we were using. There is truly no comparison in terms of reliability. The list of mechanical repairs for the entire fleet is so short I'll list them in order of occurrance right now... Rubber Brake Line Burst, AC Belt Snapped, Radiator Cracked, Radiator Cracked. We've bought these trucks used with 100k on them and owned these trucks for around 3-4 years now and driven some of them over 100k+ miles and that's all that's gone wrong.
LCF's are known to have great turning radius's which is quite handy for portable toilet service, however when compared to other LCF's like the UD & Fuso the Isuzu turns slightly worst. However it's still much better than a standard truck. It's a bit easier to get in and out of than the other LCF's out there and the cabin is a bit roomier especially when compared to the UD. When doing maintenance/repairs (how little they are with this type of truck) it's very nice that the entire body of the truck simply lifts out of the way of the motor, this makes the entire engine completely clear and easy to access any part of, very very nice indeed.
Another common complaint I hear of these trucks is that they are slow, this truck isn't a power stroked speed demon but it's certainly sufficient in most scenarios especially in hilly California. I would definitely say that if your going to let an employee drive than this truck certainly will keep them out of trouble, speeding causes accidents anyway. The truck is slightly faster than a pre power stroked (turbo) 7.3l ford Diesel.
Fuel economy is surprisingly low at around 12mpg and because your riding over the front wheels it's a bit rougher than a comparable F series, however you do get much better visibility and maneuverability than most other trucks on the road. One worry however is that because your sitting literally at the front of a vehicle the crumble zone for a head on accident is almost non-existent.
Isuzu also makes a Gas version, though gas itself isn't that practical its suitable for a CNG conversion. A couple of tanks and a regulator later your buying fuel at $.80 to $2.00 a gallon, a huge savings compared to gas & diesel, much better for the environment as well.
In conclusion, I'm surprised that this is such a rare truck for portable toilet suppliers, this truck has everything a portable toilet operator would need and then some. Portable toilet truck manufacturers take note this is the truck you need to be designing tanks for.