Sure do. I'm well aware that it's not the same as being on the fells, but it's constant hard work, and measurable.
On a constantly uphill session, looking at around 3000ft/hr on a hard treadmill session. On an interval session like last night i manged just over 3000ft in 90mins. On a stair-climber session can push out around 4000ft in a steady hour.
It isn't interesting, but it's hot, hard work, and has certainly helped me improve (along with club sessions trying to chase faster runners!)