I have tried Scrum. I have also tried various pick-and-chose hybrid approaches which were generally less successful. For example having scrum-like sprints and daily stand-up, but still having a fixed feature set and fixed deadline. This doesn't really work. (You can have deadlines in Scrum, and you can have fixed feature set, but you cant have both!) This happens if management does not really buy into the process. The place where scrum worked was because management was willing and able to try something new and willing to learn.
For what it is worth, I have also seen classic waterfall be successful. But I have also seen several big-scale disasters with waterfall, and in my experience waterfall carry much larger risk and is much harder to salvage when it goes off track.
