Fwiw I used Bristol as well as CATS QB for my last minute revision.
I did not complete all the questions due to time limitations. I did pass all the ATPL Theory Exams first time, so I can't be accused of memorising the answers.
Bristol was easy to use, and if you pay extra you can be sure of covering or and new syllabus. I just used the old one. It has a user friendly interface and the explanations are really helpful.
I also used, and cannot recommend enough, the CATS iPhone app. It's something like £15. It covers all the subject areas. It does let you revisit the questions you got wrong. On the downside it doesn't track your continuing progress like Bristol, and there are no explanations. On the plus side, there are no explanations, so you have to go and find out for yourself, with means you are more likely to know what you're talking about (although this doesn't help with the questions where you have to select the least wrong answer...).
The main benefit of the app is that you don't need to be connected to the internet or use a computer to access the questions. This meant I could do questions on the train, in the doctor's surgery, surreptitiously during work meetings and last thing at night before going to sleep. For that reason, despite its limitations, I still think it's worth every penny.