HWD,
Two very important points. First of all, what makes a good school will vary from person to person - I can only comment on what I looked for in a school, others will have different priorities. Secondly, the things I'd look for in a residential course are not the same as the things I'd look for in a distance learning course.
Having said that, here's my personal opinion:
For distance learning, the single most important thing is the quality of the notes. No, all schools' notes are not the same. Do the notes use diagrams to explain tricky points? Is the language used in the notes clear and concise? Do the notes assume some prior knowledge which you don't have? (Or, conversely, do they spent ages labouring over things you already know?) Is there space along the margins for you to add your own comments? Is the paper of sufficient quality to be able to withstand you leafing through it time after time? The list is endless.
Apart from the notes, the responsiveness of the school is important. You are not on your own for distance learning - you have a school full of instructors sitting there waiting to help you if you need it. At least, that's what you would hope for... If a school is going to take two weeks to reply to a query, I'd look somewhere else.
And, although I didn't realise it at the time, the standard of the brush-up course is vital. Not much way of knowing how good this is, though, except by speaking to others. (I wonder if schools would allow you to sit in on a brush-up course for an hour or two? I've got no idea - it's not something I thought of until just now!)
That's for distance learning. For residential, the priorities would be different. Since most of your learning will be done in the classroom, the standard of the instructors, and the instruction given, is the most important thing. As with the brush-ups, this is very hard to tell in advance except by reputation. The quality of the notes is far less important than for distance learning, and the responsiveness is pretty much irrelevant for a residential course.
Then there are factors which are common to all types of course. For some people, the cost of the course will be an overriding factor - either to be considered alongside other factors, or to the exclusion of all other factors. Other people might be concerned with the length of the course. LGU seem to be the most innovative of the distance learning schools, with a brush-up course which is half the length of all the other schools (which was enough for me to seriously consider them when I wouldn't have done otherwise). I believe that since then they've added an alternative course which is split into 3 modules instead of two (not certain of that though) - this might suit some people.
Multimedia "gimmicks" will depend on the individual. I'm with you - I can't learn from a computer screen. But although I've barely looked at the notes on the Bristol CD, I've made lots of use of the computerised progress tests. Others will have different ways of studying, and might find the computerised notes more useful than the tests - it all comes down to the individual.
Hope that answers your questions!
FFF
---------------