I used CATS distance learning, got on fine (first time passes all subjects taken within 9 months of each other) - that's as well as full time job plus a couple of other part time jobs etc etc.
I think any school is what you make of it. If you put the effort in you'll get the results back out. If you're able to self motivate there's no reason why you shouldn't get decent results with CATS. What is good is that responses to email questions are usually pretty quick, the full time team are really knowledgable and the guest lecturers are a good laugh as well as being able to impart a real sense of what's happening out there in the big wide world.
I haven't heard of any school with a really bad reputation, so I would weigh up the following issues:
1) How many groups of exams does the school use? Some work to two sets of sittings, which works well for some people who want to get the pain over and done with. Others use three, which spreads the pain but works better for getting leave from work etc.
2) Where is the school relative to where you live? If you can pop in easily, that's a good thing, even for distance learning.
3) Costs - what do you get for the money? I bought the books too so my course cost £1600. That also included the full online versions plus study notes plus the in-house online question bank etc. I also used one of the other well known question banks, and the CATS IPhone app.
I still have my books, and in fact will be returning to them this week to brush up for a small project I'm working on, so I'm glad I have them.
Colleagues also bought material from other schools to use. Sometimes one explanation makes more sense than another explanation, so it's useful to have other versions available. I noticed the same thing going on at other schools I've visited including some of the more expensive ones, so it's not an indication of a failing. I think it's more to do with human nature and one text book isn't going to be able to explain everything to everyone in the way that each individual relates to.
Another colleague is presently using the Pro-Pilot App and seems to be getting on well with it. It looks very shiny and lovely and I think the animations are good for some concepts. But it still suffers from being a single explanation, so if something doesn't click you're still going to have to look elsewhere. Plus you pay extra for the shiny niceness. If you can afford it, and it sounds good to you, do it. The whole process is pretty painful, so anything that makes it easier has to be good.
I am trying to keep my costs to a minimum, within reason, hence the choice for CATS with books. I don't regret the choice of school or buying the books, even though they're now technically out of date since they're JAA and not EASA - most of the stuff that matters (Bernoullis!) remains the same. Don't forget the exam fees add around another £1000 plus there are accommodation fees for both the brush-up courses and the exams.
Good luck with whatever you decide.