This may be a bit of an archaic approach, but I've discovered that a lot of the do-dads that are added onto systems turn out to bite you in the butt. That's one of the reasons why I prefer the simpler setups that have fewer things to go wrong. The Old Air unit I installed was a bare-bones system with a simple mechanical actuation control cable as opposed to an electronic control module. A filtration system in an AD truck might be something to consider, but it's not going to sway me in that direction, unless I know it really works and isn't going to cause me issues. The evaporator size in the add-on A/C systems is relatively small and you really have to move a lot of air through them to keep everything balanced. I've found that many inexpensive underdash evaporators need to have a lot of air moving and the air movement im the cab is like a mini-tornado.
In reality, I really rather drive with my windows down and enjoying the feel of an open vehicle. The cowl vent gives me great air flow through the cab and the split rear window lets the air flow with very little interior wind noise. The a/c is nice if you're stuck in heavy traffic but in my particular case, I wouldn't rate it as a "must have." But then, that's just me!
Dave
