After reading plenty of bad reviews about this shuttle service, I was hesitant to book with them. In the end I decided to give Super Shuttle a try anyway, since, let's face it, people that had bad/horrible experiences are much more motivated to sit down and actually write a review. The thousands that received good service often don't publish their experience.

I booked the Shuttle Service online, and did NOT add gratuity there since I feel rather uncomfortable not tipping someone directly. (Instead I tipped the driver when he dropped me off.) No problem here.

I landed in Newark airport, and got lost looking for a Super Shuttle counter. Come to find out, there is none, you have to call them from a sort of phone station.
I ended up not having to do so, as I ran into two Super Shuttle drivers along the way. They told me they were waiting for two other passengers, and that I could come along. After about 10 minutes, the two others arrived and we left. The shuttle stopped at several different terminals to pick up additional passengers. Quite frankly, I'm not sure why other reviewers seemed unaware of this, but it is a shared van kind of service. Of course they fill up the van first before they leave, otherwise they wouldn't be making any money with their service! (Oh, I forgot to mention, I paid $19 each way.)
After the van was full (which took about 20 min of driving around and picking up other passengers) we left for Manhattan. I was dropped off at my hotel about 1.5 to 2 hours after landing.

My return shuttle to the airport arrived on time at 4 a.m., and after a few detours to pick up more passengers were were off to the airport. No problem here either.

Both drivers were nice and drove in a responsible manner. I might have just been really lucky here considering some of the other horror stories, but I'm going to book Super Shuttle's service again on my next trip.

I think it just really helps to inform yourself before you book. Yes, it is going to take you longer to get to your destination than with a regular cab, and yes, you will be squeezed into that van like a sardine, but in return you're only paying $19 each way. That's a fraction of what a regular cab would cost!