Roofing underlayments—worth the extra hassle or just hype?

Just finished putting on a new roof, and I decided to spend a bit more on one of those leak-resistant underlayments. Guy at the store swore by it, said it'd save me headaches down the line. Honestly, installing it was kind of annoying—sticky stuff everywhere and took longer than I expected. But now that it's done, gotta admit it feels pretty solid up there. Had some heavy rain last weekend and didn't notice even the smallest sign of moisture in the attic (which is a first for my old house). Still, I'm wondering if it's really worth the extra cost and hassle in the long run or if regular felt paper would've done just fine.

Curious if anyone else has tried this stuff out—did you notice a real difference, or is it mostly marketing fluff?