Last year I switched from knobbies to slicks, and it was a revelation. Smooth, quiet ride, feeling like you are on rails, etc.

Recently, I've been exploring unpaved roads and rural tracks, in addition to my regular street commute. The 1.5" slick tires have performed very nicely on my 26" bike. I've learned to shift my weight from the front to rear as the ground demands it, to avoid front-wheel slipping or to preserve traction on the back. Basically I practically never get uncontrolled skidding anymore. The only times where I've wanted a bit more traction is with very muddy/soft ground, or with very loose and big gravel going uphill.

So my question is, just when does one "need" to switch to knobby tires? I still have my old tires lying around, and I guess the anxiety comes from seeing them gathering dust.

(Maybe I should just get off my lazy bum and switch them, and give them a try...)