Ok, I'm going to take a stab at this:
Full Sized Vans for overall quality I like the Ford Econoline. It'll get crappy gas mileage, but they've got pretty much all the kinks out of it, and you should be able to get over 200k miles out of it with relatively little headache.
If fuel mileage is an issue (and you still want size) get the chevy with the 4.3l V6. It'll get slightly over 20 mpg on the hwy. The transmissions aren't that great, but keep the fluid changed regularly and you should be alright. I have a couple DHL delivery vans that I service with 250k+ on the original transmission and engine.
If you like to look good. Go for the Sprinter Van. I have several customers with over 300k miles on them (original power train) but it takes about that many miles to have it worth the extra $$$ they cost.
I have several customers with the HHR, they don't get the mileage of the Transit Connect, but bang for the buck it might not matter. The engine/transmission has been around for a while, so they are relatively easy to service. But they aren't the strongest in the world to hold all that weight.
The transit connect: its a motor they've been running in their rigs for years, however the transmission is relatively a new design, so I'll be curious to see how it holds up with time. Most of the customers I have that drive these rigs really like them, and buy another.
With the potential for fuel costs to rise, I think most people in the service industry should reconsider what they actually need to stock in a service rig, and what they can make special trips for. I get nerdy when i buy a new rig and build a spreadsheet that accounts for depreciation, fuel mileage (with fuel prices as a variable) and maintenance and I break it down to cost per mile (or cost per 100k miles.)
If I had to do it myself I would buy mobil 1 oil from wal mart. Run either a purolator pure one, or mobil one filter, run one of these for a drain plug
http://www.fumotousa.com/ ... and i'd change the oil every 5-7k depending on highway miles and engine burnoff. If your guys go longer on the oil change (because they don't care its not their car), the oil should be able to take it.
Been owning/operating/running oil change stores for 16 years with a few hundred thousand services under my belt. And a lot of talking to owners' about their rigs. So I'd appreciate feedback if it differs from mine, but honestly, I probably won't pay much attention to it.