no

+1

Effort level and duration are what give you improvements.

A regular distance/speed computer is kind of nifty to have, but shouldn't be used to guide your training. HRMs and powermeters are just ways of quantifying effort level. But you can measure effort level the old fashion way ("doesn't hurt", "hurts a bit", "hurting now", "hurting lots").

i have 2 or 3 upstairs in my bike room, but haven't used one in about year. i wear a watch but that's it. back to basics. i just find them distracting, and just go by time and perceived effort.

i think numbers can make you go harder. for training, until you get used to spinning, a cadence meter is really handy.

i find that my preceived exertion depends on my mood, whereas HR will tell me my body's actual effort

a method of keeping track of time is very important for training

not necessary but i think faster progress
not talking about avg. speed and stuff
but HRM and power

Ditto....I have one, $40 from my LBS. Cadence is SOOO important.