That depends on the meditation - it's never quite the same, really varies a lot. Now, I've taken to doing a lunch time meditation in the tinted back seat of my car (secure carpark) and some times I've actually nodded off for a fraction of second or two - or who knows how long.

At any rate if I was disturbed between the 10 and 20 minute mark when I typically start to settle into it I'd feel a bit rattled. You're meant to spend a minute or two getting back, slowly stretching out and opening the eyes. Always feel a bit sleepy, but then also strangely refreshed.

As a programmer I do find slowing the "mind storm" rather beneficial. Definitely feeling less frazzled.