I just finished up handgun I-III on sunday and let me say, Holy Schnikes. I thought I knew how to handle by gun before... I was wrong. They
significantly refined my drawstroke, presentaion, grip, stance, trigger management, reloading... pretty much everything. And that's just the skills they improved, that's not counting the new ones I learned: shooting on the move, shooting from cover, gooseneck grip, cutting the pie, drop outs. I learned a lot. I will definitley be back for IV-VI.
If you're on the fence about going to TDI, GO. It's worth every. single. penny.
Just in case I didn't make it clear, I'm officially a TDI fanboy

“How a politician stands on the Second Amendment tells you how he or she views you as an individual; as a trustworthy and productive citizen, or as part of an unruly crowd that needs to be lorded over, controlled, supervised, and taken care of.” -Suzanna Hupp