The Centers for Disease Control and Prevention, or the CDC, recommends people get the vaccine as soon as it becomes available.
I just got mine today, and while I always forget how sore it feels the instant you get it, the pain - if you'd even call it that - goes away almost instantly. At least it has for me.
It's one of those things I look at as hey, it can't hurt - and it might just help - so why not?
The pharmacist who gave me mine said this year's vaccine protects against influenza A, influenza B and the H1N1 virus. Of course, there are strains not included, so it's not a 100% guarantee you won't get the flu - but again, why not?
Which leads me to my next thought ... There are a few people who can legitimately answer the "why not?" question. According to the CDC, people who shouldn't get the vaccine include those with severe allergy to chicken eggs or who have had a severe reaction to a past flu vaccine.