I took a PR course before writing the October LSAT... Overall, it was just OK.
Starting with the positive: For me, the course was helpful because it forced me to get out of the office (I was working really long hours at 2 different jobs) and to really focus on the LSAT. I also liked that we wrote a full proctored LSAT almost every weekend during the course, which was good practice - especially because similarly to what you found, when I practiced on my own, I got really high scores, but when I actually wrote strictly proctored tests, I tended to score lower. One of the instructors I had that taught the games sections and conducted the 1-on-1 tutorials, was great - he really knew his stuff, was quite good at teaching it, and I learned a lot from him.
Now the negative: You have to be very careful what instructors you get. In my case, the games & tutorials guy was awesome. In contrast, the guy that taught reading comprehension and arguments sections, was quite awful. He obviously knew how to do well on LSAT (otherwise there's no way he would be at the school he's currently attending), but the guy really couldn't teach. Having paid about $1200 for the course, I was not thrilled with having him answer my questions about difficult problems by saying: "...ya, I thought that was a hard question too..." Also, there was a very wide range of abilities and understanding of the material in my class, so it sometimes got frustrating when certain people got stuck on what seemed like really simple problems and held up the entire class over it.
As for whether it helped: Taking the course was good in terms of developing a strategy for approaching the LSAT instead of just going randomly at it as I did when practicing on my own. We also got a ton of practice material that was all taken from real LSAT's. At the same time, when I wrote the LSAT, I only got a 163, whereas by the end of the course I was pretty consistently scoring about 170. I really couldn't tell you though, what went wrong there or whether that was the result of the course or something totally different...
I've heard good things about Kaplan or Power Score prep courses. You might want to look into those before choosing PR, but whatever you do, good luck!