To the original question, I do recommend Sierra.
When sifting through opinions, a few seem to remain constant. Sierra is expensive - primarily due to location. Not too many will argue that this is a prime location. The best way to keep expenses down is to progress rapidly by making the most of every flight lesson. The surrounding area is also expensive to live. Many are able to share housing for close to $300/month (not me, I have to pay $900/month for a place big enough for the family). Also, choosing the 152 makes things much cheaper. The previous post did a good job of giving you the rates, the rest is up to YOU.
As far as people leaving, that seems to be true. However, almost no one was leaving pre-9/11. Sierra has continued to train as usual, and yet students are leaving. Common sense tells me that it has more to do with a difficult hiring future than anything else. That's really too bad for those who have quit. Some have left because of being fed up, run out of money from poor planning, tough program, and (I think) primarily due to the overall aviation outlook has shifted to mid-range instead of the short-term (pre 9/11). It has become a matter of maintaining your focus.
In regard to the 'tough' program, it's really as tough as you take it. What I mean by that is, if you progress at a relaxed pace, its not that tough. But if you try to get through the ratings quickly, it can make it tougher. In essence, toughness is proportional to your pace.
Most also agree that the training is of good to excellent quality. As said in previous post, walking up to an airline saying, "Hi, I was trained @ Sierra" will not get you a job. It's the quality of training that is giving Sierra grads the ability to perform well in these interviews, and therefore, fare well - even in this tough hiring market.
You can PM me with any specific Q's you might have
Hope this helps a bit.