Tom how're things.

Too much pressure on the knees, in the LONG term, may damage the knees . . . Round about 60-70 revs per minute feels right.

I chose a Specialized MTB Hardrock (bottom of the range) just because I wanted one for years and so eventually I bought one. Although, sensibly, for the commute a 'travel' type bike would be more suitable in terms of speed and efficiency . . . However, I love it and have benefited from the exercise for the past year, come rain or shine :-)

You are right about other commuters on the road . . . I 've noticed a lot since I started my commute too . . . from all ages (up to 60 yrs I guess) and all year round . . . I get up at 05.00 and start work at 06:30 . . . In the Spring/Summer it's easy . . . but in Winter it's challenging :-)

I'll write more.

Take care.