I'm not a fan of the whole mashing=injury myth though. Fixed totally gives the lie to it, and received wisdom from the heavy duty fixed riders is that fixed is slightly positive for knees.
Oh, agreed. It's not low cadences that are a problem, it's just that the forces involved can aggravate all sorts of existing problems, which may or may not be solvable. I have a long-standing patella tracking issue that I've noticed objects to mashing a lot less that it used to (that is, I can actually mash now, I never could before) since I've been using clipless to preserve correct foot alignment and have developed my quads through cycling. My ITB thing seems to be a combination of poor pedalling technique distinct from, but perhaps encouraged by, mashing and having legs that are different lengths. I suspect it's become a problem now since the amount of force I can deliver is no longer limited by the patella issue.
I can see how fixed would be helpful for learning to deliver power evenly through the pedal stroke, but we have hills here and I like my gears too much. Anyone suggesting a S3X will be shot.
As for small gaps at low speed, I find the key is not to panic. I actually find the Streetmachine is in some ways easier than an upright in that sense, because although it's long and rigid, I have a much better intuitive feel for how wide the handlebars are. That doesn't mean it's particularly well suited to weaving through gaps, of course, but I do have a reasonable idea if it'll fit. On an upright, I'm much less confident about the bar width (which is why I'm a complete chicken at filtering).
Successful emergency dismounts are a valuable skill in themselves, of course.
