I've done two of them, Racetrack 2 level at Misano and Imola.
It's pricey but "worth it" in that it gives you the opportunity to ride a fantastic track (I assume you're thinking of doing it in Europe) which would otherwise be quite difficult to arrange, with everything included - bike, suit, even boots helmet and gloves if you need them. You literally just show up with your ID and ride. It's structured to alternate between track sessions and feedback session, as is every school I think.
The instructors are of fantastic pedigree, I was on track with current and past top-level racers and champions - Bayliss, Canepa, Poggiali, Polita, Marchetti, etc. However while they all have top credentials, to be honest some are better instructors than others. But, at least with all of them you get the opportunity to get a tow around the track from someone truly fast.
I found the groups themselves to be somewhat slow, I think DRE participants tend to over-estimate their ability when signing up for their level more than people do at track schools I've been to in the US.
And, the groups run a lead/follow format I find frustrating: the instructor leads, followed by the five people in his group. After each lap, the group rotates so that someone else is directly behind the instructor. BUT, rather than have the lead guy of five drop back to the end of the line (and everyone move up a spot), they have the END guy pass all the others and move up to the front. In my opinion it would be much better for everyone to simply move "up" a spot (and the previous lead guy drop back to the end).
Overall I would say it depends on your level and what you're looking for. It's a great experience, but won't give you as much raw instruction/improvement as something like the CSS. But of course they don't run the CSS at places like Imola, Assen, or Mugello.
