The darcey bussell one is really nice. It's more relaxing and stretching than hardcore, if that makes sense. I really enjoy dong it after a day at work, the music is lovely and relaxing. The only thing I'd say is that she expects everyone to be as flexible as her; annoying but I guess it gives you a bit of motivation!
Lynne Robinson every time, she has been teaching pilates and training teachers for years, she explains everything really thoroughly. I go to classes by a teacher from her training school (Body Control Pilates) and it is excellent.
I've only got a couple of them now, I used to have a few on VHS bur I got rid of them when we ditched the VCR. The one I have used most is Pilates Powerhouse. I haven't used it for a while as i have been going to classes but it is good.
I go to classes taught by physiotherapists who are part of the Australian physiotherapy pilates institute - they have videos (just google APPI). They aren't as trendy as some, and may seem fairly tame to hard core Pilate fanatics but I quite like them. But without actually going to classes, I wouldn't have had a clue. It's easy to do very little or do the movements incorrectly so the prompting is fairly key...
You can rent them (amazon, libraries) etc so you can always try several different flavours. It may be cheaper just to buy 2nd hand off amazon/ebay but the postage adds up..
If you have a bad back you need to be careful. I get intermittent sciatica and piriformis (sp?) pain, I did a lot of classes for a few years pre-DCs (10 or so years ago), which did help then we moved house and I couldn't find a good class so I started using the Lynne R videos/DVDs, they also helped. I let it all go once the DCs were born and found my back was largely sorted by wearing orthotics in my shoes. However I found the Body Control classes in my town this year and started back up with those. The instructor is brilliant at modifying the exercises for peoples injuries and ailments (I also had a prolapse dating back to childbirth, for I have just had surgery, which is another reason for caution, Pilates done incorrectly or over strenuously can put too much strain on the pelvic floor).
I would say that anyone with any sort of pre-existing injury should start out with classes, and they should be with a dedicated pilates teacher rather than the sort you get at leisure centres run by the general fitness instructors. My instructor comes round and moves (for example) your leg, ever so slightly and it makes a big difference.