I have 4 of these lights from the 300, 650 and 800 and really like the small size good light power, decent battery time, and easy mounting system. The latest 800 has a bit of a downgraded strap that is oilyslimy so harder to attach, and there was a missing screw on mine that I am hoping to get replaced to light does not slide right off the mount as it does easily without the screw. Overall a great little light and I highly recommend it as a city light or backup to a dynamo etc. Probably not strong enough or wide enough light pattern for all night MTB rides or even dark country roads, but with a dyno and this or several Urbans, that works great.
The touch screen is not very responsive-sometimes I have to touch the screen many time for it to respond. The HR monitor is better than the old one. I do like the auto upload feature via wifi so my rides get to Garmin Connect and Strava before I even get into the house.
I've used the PD-8 (disc version) on my commuter for over a year now to power front and 2 rear lights, works great, no more changing batteries. I purchased a PV-8 and built a front dyno wheel for my wife's upcoming cross country ride (bike the US for MS !) so she could charge her phone, camera battery, etc using a Sinewave Cycles USB adapter. I'll update the review after her 4295 mile ride this summer !!
Light, barely noticeable drag, builds up well. All at a ridiculous price point. Not sure how SP does it, but it's almost like cheating. I've had them on both of my bikes for a few years now. A total no brainer for a commuter bike.