OAT is a good school. It is very expensive compared to the others, and not having qualified from any other school I couldn't say if it was worth the extra cost or not. I was happy with my training, but it hasn't helped in finding work. At the moment, experience is by far and away more important than which school you trained at, and if things don't improve, all that extra money may be better spent on extra hours or something like an instructor rating.
OAT do have something of a reputation for substantial bull!!!! to get you to part with your cash and sign up (it is something the marketing department excels at), and I would be very wary of any promises made about helping you get a job. The careers development guy is a nice chap, but has an unhealthy preoccupation with Ryanair and this seems to be the limit of assistance current graduates will get. Don't expect anybody to place you in a job, it will only come from your own efforts. Don't fall for the old line of "come to Oxford and we'll help you get a job" - they can't and probably won't.
The current APP scheme is very expensive, far more expensive than the course I graduated from, and I'm not sure what OAT can promise to justify the extra expense. A fancy selection procedure to get on it may only be more marketing to give it an exclusive appeal and back up claims of better employment prospects.
The instruction - ground and flying - is generally very good, but like anywhere else, there are individuals who don't meet the grade. You may be unlucky and get a poor instructor who will cause you a great deal of frustration. The organisation/planning can be poor and this is generally where the frustration kicks in, but now the school is unable to rely on healthy numbers of sponsored cadets and must make its money form self-sponsored students (hence the price rise I imagine), things may improve to your benefit. The marketing department can no longer trade on its airline sponsored connections.
If you go to OAT you won't be disappointed by the training, but you may find a huge gap between reality and what the marketing people promise you today. Proceed with caution.