My mum got called up last year. She deferred it once as she was going on holiday. She had to do it a few weeks later.
I previously always wanted to get called up as I thought it would be fascinating, however, mum got put on the jury for a quite harrowing child abuse case. She found the details extremely difficult to listen to and felt a huge responsibility to ensure that the right result was got for the victims. They found the bloke guilty on all charges except for the very first victim to come forward, due to some technicality, although they all agreed that he had abused her, and my mum felt that they had let her down.
She had to listen to stuff that this man had done to children aged around 5yo and having a granddaughter the same age, found it very difficult.
The case lasted a week and she was stood down from jury service for a second week due to the harrowing nature of the case they were on, the judge did not expect them to do another week.
If I were called up now, I would find it extremely difficult to manage with childcare before and after school. The trains are erratic. There are no childminders here. I am a single parent with DD's father living 2.5 hours away so no help from him ever. I am self employed, so would probably lose a lot of my earnings, as they never pay enough to cover what you actually lose. I could not be on a case that lasted for 8 weeks as I would not be able to cover my work for that length of time. I have weekly and fortnightly clients and there is no way that I could not do that work for anything longer than 1 week.
So whilst I think it is a good thing to do, I do think that it should not be compulsary if it would cause extreme problems to your own life.