Ours was outstanding in its last Ofsted and I can see why - they are very professional and do everything properly (ie the babies' books are filled in every day without fail, the learning journals (or whatever they are called now) are always up to date, the weekly newsletter comes out every week without fail etc). In the weekly newsletter you can see that they plan their activities around what the children are interested in.
But the most important thing is the staff - who are all very good and very caring, very very low staff turnover. It had a wonderful atmosphere when I visited and I still think this is the case 2 years later. However this would depend completely on the nursery itself rather than the chain. I don't think you can judge any nursery without visiting it.
We also use another nursery, a small independent one, so I have a point of comparison.
2yr old DS is at a Teddies and we're very happy with it. The carers seem invested in the kids, they have great activities day to day and also have a group that brings animals in (snakes, rabbits etc) which DS loves. All in all, it's been a really positive experience.