Engine reliability? though the E model is a slightly smaller motor than the current R.
They changed out all the 690s as far as I know, from 650 (mine) to a full 690cc. Nothing crazy - though it is wise to keep an eye on the exhaust rocker. There's an auto-decompression device that seems to be not so good for one of the bearings on that rocker
What about ease of maintenance? I.e. how hard is it to get to the battery, airfilter ec.
Very easy to get to both. Remove seat and the battery is there as it the filter lid which is secured by two bolts. Oil changes are a tad fussy as they use the paper cartridge filters in a horizontal recess - so you need to fish them out with a pick or punch a hole in the end and hook 'em. They won't just drop out
Any long term issues? I know the 690R models had that left side crank case bearing issue resolved, but any other known ones?
Early ones needed new fuel filters very very early. Like a couple thousand miles early. If left too long they resulted in burned out fuel pumps.
Hows the FI? Clean smooth and responsive?
It benefits from some tweaking. The O2 sensor makes it a bit jabby at low RPM low throttle combos. Also *needs* remapping to run any lest restricted exhaust lest you enjoy stalling.