I did it this year. There was a lot of waiting around, which was due in all cases whilst I was there, to the defendant pleading guilty at the eleventh hour – the case did not require a jury then. Once you're on a case it can be very interesting, and as someone has already mentioned, if you are appointed jury foreman as I was, it is satisfying, and more so that you are making a difference.
I'm self employed too, and it wasn't a problem, I was available for two weeks but only went in for one all tolled. So I managed top get quite a bit of my work done during that time. They are quite reasonable, and ask if the case is likely to go on for more than two weeks, if you can make it. If you really can't do jury service you will be excused – but I'd say if you can – do it. It is one of those life experiences, and it was in my case very rewarding.