The has some slow patches and fast patches, more extreme than the IRT I'm pretty sure. It's not just the timers; there are a lot of steep upgrade and downgrade sections of the route. The from 14 St to 59 St is noticeably slower because of the timers passing 23 St and 50 St, but I don't think it could exceed 35 MPH even without them, because of the upgrade. Passing 50 St was only 30 MPH before the timers were installed. CPW northbound is downgrade as has been discussed, and could be 50 MPH northbound without timers. 59 St - W 4 St is a pretty good stretch, and 45-50 MPH is possible coming southbound into 42 St.
In Brooklyn, there are a lot of steep upgrade sections, and all of the steep downgrade sections are timed. That's my judgement. Yes, the timers into Broadway Junction and Utica Av are annoying, but aside from that, it's reasonably fast (30-35 MPH generally).
If I'm correct, the IND was designed with steeper grades because the newer IND equipment in the 1930s could handle them better than IRT or BMT equipment. Thus, the IND could be built closer to the surface even if there are hills and such. Problem is, with the braking issues raised after the big crash, timers have been installed on many steep downgrades...
Well, that's what I've got to say about the line.