I know you are asking about
Alamo, but I was hoping to get your opinion on Dollar as you mentioned you use them normally.

I have a ressie for a minivan from Dollar for June 17 to 26th for $411 (I still have my fingers crossed the City Specials will get better before our departure). Did you find Dollar good to deal with? The vehicles in good condition? I signed up for Dollar Express but was wondering if that was more of a marketing thing than actually something to speed up the process.
I will try to address your questions, as well as a couple of others in the above posts.
My experiences with Dollar have always been good. No problems. Nice vehicles, clean, never any problems. I am not at all picky about the cars, though. As long as they run and don't smell of smoke. Also, we have often been upgraded (free of charge) from full-size to mini-van. But, of course, you can't plan on that. For us, the full-size is fine, so I reserve that, but I believe 3 out of 4 MCO rentals, we were upgraded to mini-van.
The first time I used them (2005), I didn't know about Dollar Express and we waited in line in the terminal at the counter for about 30-45 (precious WDW) minutes. I was having an anxiety attack. I kept watching as person after person cruised through the Dollar Express line. When we returned from that vacation, I read on these boards that anyone could join Dollar Express (free and easy).
Since then, have used Dollar Express many times. In Orland, summer, weekend, Dollar Express line was always shorter than regular. Usually takes me less than 5 minutes.
Counter vs. Kiosk:
Within the airport terminal, below baggage claim are several rental car company's rental counters. For Dollar, there are two entrances (lines): one for regular and one for Express. The Dollar Express line is (usually) shorter and faster b/c they already have some of your pertinent information. Either way, after waiting in that line at the counter and completing all paperwork, showing ID, signing forms...you then take your paperwork across the street and into the garage and find the appropriate rental company "kiosk" (small hut within the garage near their cars). You present your paperwork to the person at the kiosk who checks it over then assigns you with your car and your off...
BUT, if you are a Dollar Express customer, you can complete much of the 'paperwork' on-line ahead of time (things like driver's license info) and you can skip going to the counter and go straight to the kiosk. It's a time saver (maybe only 5' but can be more).
I am not sure about the Alamo (vs Alamo Insider) process, though.