I am entering my 8th season as a Celtics Season Ticket Holder. I order a half season package and love it. Over the course of two years, I get tickets to at least one game against every team in the NBA.
I am currently on a monthly payment plan that gets billed to my credit card account each month. My plan comes with 20-21 regular season games and one pre-season game. I am in the balcony, but the front row, so the seats are great.
On top of that there are some great benefits like the ability to buy extra tickets, free stuff and having my own account manager who helps me with any problems. Also, if I can't use my tickets I can post them on the Celtics Ticket Exchange and someone else can buy them and credit my account.
All in all I think it has been a great experience for me. Any problems I have had have been handled through my account manager. In the end, it is nice to get a set of games, pick the ones I want to go to and then have leftovers to sell to friends and family. Last I checked there was a waiting list, so I will look into it asap.