I went to my 10th and was disappointed, because the people I had lost touch with and was hoping to see did not come. I also felt that people fell in with the same 'cliques' we had in High School. I skipped my 20th because they wanted too much money! I don't drink, so I don't want to pay the high cost of an open-bar event.
My 25th (if we have it) will be in 2 years, and my financial situation has improved, so I am more likely to go to that one, I am hoping that as people have experienced more of life that they will be less judgmental and open to getting to know others for who we are now.
My advice to you is to dig out your old yearbook, or if you don't have it, go through Classmates.com list for your class and refresh your memory. If you come across names of people that make you wonder what ever happened to them, then go; if you find yourself feeling that you'd rather not associate with most of those people or to resurrect forgotten memories, then avoid it.