So it's rare for you to see another cyclist and think 'I'd have done that differently' but common for you to think 'that was a really sensible thing to do'?
More or less.
In the city centre, I've seen a fair bit of stuff that makes me wince (especially during term time). It's mitigated by low traffic speeds and improving cycle facilities on the stretch I ride. (Oxford Road between the car wash and Whitworth Park is much better this year, for example - traffic islands stop cars/busses encroaching on the mandatory lane (which has also been widened). Prior to that, busses would begin to move left towards stops some 100-50 metres distant, and there was a lot of iffy undertaking happening as a result. Cars would simply drift over, I guess as the driver lost focus on what they were doing). I used to see a lot of red light running on pedestrian crossings (not especially dangerous (bikes are pretty easy to avoid, at least, compared to motor vehicles) but antisocial). Can't remember much of that recently though.
The other 10 or so miles, not really. If I got picky, I'd say I've seen some unnecessary filtering, and occasionally bad road positioning. The people I've seen/see more or less every day though, I'd struggle to find fault with. There are a couple of people I wish would either call their overtakes, or pass wider (as I've moaned about elsewhere).
I doubt we've seen the surge in cycling that, by all accounts, London has though - I suspect our cycling population is smaller, and churning somewhat more slowly.