I think a total nightmare is quite an overstatement...an inconvenience, yes, but nothing that can't be settled with monitoring flights and a phone call if they do change.
All airlines will change flights - especially if you book your tickets far in advance. Delta's also been going through restructuring and consolidating flights at certain airports, etc. so changes SHOULD be expected. If these changes did not occur, there might be one less airline to choose from.
We always use our frequent flier miles for leisure travel and have not had a problem at all. In January our schedules were changed coming back from Orlando, but we knew about it and fixed it in advance with a call to the Delta office.
If the price is right, you should go for it!