Well, generally it's no big deal. A little poke, and sometimes you have some upper arm muscle pain and stiffness a day or so afterwards, minor, more annoying than anything. I've been getting one for years now, one or two times I had a very slight fever the next day or so, along with a slight sense of allover muscle/body aches, but again, very trivial, pop a couple of aspirin or ibuprofen and it goes away.

The flu shot isn't 100% effective by any means, but it is well worth it. I did get the actual flu last March, as did everyone in my office, confirmed via testing, even though I got my flu shot a year ago in October. It seems last year's vaccines was one of the least effective in a while, only about 60% IIRC.

Yup, you definitely should do it.