I read all the reviews but thought if I was prepared I could avoid all the pitfalls.  I was wrong, I was not prepared enough!  I would rent again (only b/c of the cost) but would be even better prepared.  Hopefully, you can learn from my experience:

1) LINE: was not long- however I rushed to the counter as soon as I collected my bags.  The line started to grow but not more than what you would expect at an airport

2) INSURANCE: I prepaid & declined insurance on line hoping to avoid the hassle at check in.  We were never asked if we had insurance just "insurance?" (a sales trick I'm sure) We stated we did not want insuance.  After check out, we noticed we were charged insurance.  Went to counter, they took the insurance off but then told us it was Florida law to have at least one of the insurance options (my husband choose the least expensive).  Later found out we were LIED to, you are NOT required to buy one of their insurances. 

3) CAR CHOICE:  We had a free upgrade coupon that was to be applied at the counter.  We gave the coupon to the agent & he said, "I can get you into a mini-van."  We thought OK, this is the upgrade.  Well, it turned out we were given the free upgrade but then upgraded to the minivan at a cost!!  According to another agent we spoke to afterwards, "IT IS BUDGET'S POLICY NOT TO TELL A CUSTOMER WHEN YOU WILL BE CHARGED MORE, IT OFFENDS PEOPLE."  We thought the mini-van was the free upgrade!!  Even without a coupon they will offer you a car but not tell you it is an upgrade.  Please ask, is this an upgrade & will it cost more than the car I reserved.
The mini-van was brand new, clean, full tank of gas & very nice.

4) RECIEPT:  The reciept you receive at the rental counter is very misleading.  It contains random numbers and charges.  We had a 10% discount coupon which showed on the receipt as a $20 credit but then saw a 10% charge of $56! No one could explain the 10% charge & why there was a difference b/w the credit amt & the charge amt. 

We dropped off the car at the end of our trip & was charged $250 in addition to our orginal  $197 on line cost.  We went back to the counter, argured with the agent very loudly & was credited for all charges over the original $197 (still keeping an eye on my credit card as I do not trust the agents).  We asked for an explaniation for EVERY charge, there were several fees that could not be explained. 

Trust NO ONE, do your homework, order on-line & make certain at the counter you ask after question/comment from the agent, "will this cost me more?'  I would not use any coupons at the counter as it gives them an opportunity to scam you.  The price is 1/2 of what you pay at other rentals so if you have time & the ability to stand the constant hassling at the counter - it is worth the cost. 

Also, give yourselft plenty of time to return the car in case you need to argue any of the charges.  I believe they count on travelers not having the time or energy to challenge.