I teach at a school that is all-IB in sixth form and it does suit well-organised, independent learners (and those who can acquire those skills). I think it is is also good that students continue with Maths, English and a language - avenues in later life may open up with those (we had a scientist who moaned about the compulsory language - now she's at CERN it's coming in handy). Cambridge is a special case - Oxford is more realistic with points offers.
We have found that while points offers can be high, universities are more likely to take IB candidates who have missed their predictions than A level students - and the IB students have an advantage as their results come out earlier.
To me the major sales point is that it's a better preparation for university, and therefore, rather than having a massive adjustment to university-level study, IB students can enjoy their first year. Having said that, some of the features of IB -- academic rigour, public exams only at the end of the second year, restricted retakes etc were features of A levels when I took them...!
You should only consider schools with a reasonable number of IB students though, otherwise classes will be small, there may be a restricted range of options and as the poster above pointed out, staff may lack expertise.
I would have loved to do it at school, personally, as I could have carried on with a language and done Music as part of CAS rather than doing a stressful A level in it, when I only really wanted to play music.