I've used Dollar my last two trips - sign up for Dollar express and you skip the line inside.
For reference, on US thanksgiving, my flight landed at 8:15am, got a shuttle at 8:35, I left Dollar at 9:05am (and honestly, I think on a non-holiday fully staffed, it would have taken 15 min less) and checked into the Tropicana at 9:55 and walked into DCA at 10:06am.
I also like that, at this location at least, with Dollar Express both times I didn't get asked about wanting insurance or an upgrade and it wasn't some high pressure sale job. I can't stand that. It makes me feel so uncomfortable.