I used to rent a lot with Alamo. They used to offer car rental points along with frequent flier miles and often had good promotions. Now the car rental points are gone and the frequent flier miles are much reduced :-(

My worst experience with them was also once in Las Vegas, almost identical to Catman's experience. SFO and LAX can also be bad. Now I always give my Quicksilver number and use the QuickSilver kiosk. Last time I was in Las Vegas there was no line for QuickSilver and I was done in a couple of minutes. Make sure to give your FF number also when making the reservation, I do not think that the quicksilver machines allow you to enter your FF number. Incidentally, the gas tank was half full when I was about to drive away. I reported this while checking out and the agent made a remark on my paperwork.

I have not been able to find good discounts with Hertz. I think that with the new program at Hertz, it is better to get points than airline miles (points can also be converted later to miles). As others have reported, their #1 Gold service is really good.