In reply to OP,
Time does run far too slowly on a treadmill, like it does in a swimming pool, so I only use them when the weather is really terrible or if I want to run fast, or do intervals, both of which I find easier to do on a treadmill than when outside.
To make it bearable, I often wear headphones and I use my heart monitor, though I never know what to make of the numbers afterwards. Doing intervals makes the time pass more quickly.
I use the gym at work, at the end of the day and try to do one treadmill session a week, to help my speed, but in fact do it less often. The choice, when I get there, is between going outside for a five mile run, through the local town which I quite like and know I can do, or going into the gym, and its world of tattoos, mirrors and muscles where I may well find all the treadmills occupied by slow walkers, or a queue of tut-tutters when I carry on past the regulation 20 minutes. Going outside seems a more attractive option.
The treadmill has definitely helped me to make myself go faster when outside. I could very well plod along the whole time at somewhere between 8:00 and 8:30 pace, but seeing that I can (just!) keep up sub 6:30 (15 kph) for 8 k on the treadmill has made me push myself to regularly do some sub 7:30 miles when outside.
I did fly off the back once.