I found it very useful... I have been dm'ing for around 20+ years or so (with some long breaks in there) and really found the section on Companion characters vital for mt group, as we only had 4 players and I wanted to run a module, but didn't feel like adjusting all the encounters.
I also found some amazing concepts like using Vignettes and "typing" or "profiling" your players in order to create a game that appeals to all of them. (Edit: Just thought to mention, the vignette concept has brought a LOT to my game, just by itself)
Many DM's (in forums) have commented that this is the best DMG ever printed in history of D&D. I would tend to agree... but YMMV, so it would be worth flipping through first if you can.