I have had discussions with many game players about joining in a beta of the game they are playing or a new game they want to play. I find that the thoughts run about 50-50 for or against. I personally like being in a beta. I enjoy testing out game play and finding bugs so that when I start playing the live game it works. It also gives me a small sense of accomplishment in helping to get out something I really enjoy doing.
Other people do not want to spoil the excitement of seeing the game for the first time and still others like to get an early jump on strats to beat the mobs. I try hard not to see all of the game or areas being released so I still have some surprises left to explore. Still other people find it a waste of time and feel that the companies do not listen to suggestions. I find working with developers interesting and offering suggestions that may be implemented exciting.
If you have never tried a beta, I recommend trying one at least once. You may find you have a flare for games and who knows you might find a new career.