I’m documenting my Freeflow build here: Carn Bikes frame #3 - Freeflow e-hardtail
My experience with Freeflow so far has been very good. As a hobby builder, I was a bit uncertain on initial contact as I’d heard other manufacturers were generally difficult to deal with for non-trade/volume builders. I even had trade accounts with Yamaha and Shimano distributors through my little workshop side hustle and still couldn’t just go and order a complete system.
Email response times were a little slow at first but they did reply and, having made initial contact, were subsequently much quicker to respond. I ended up buying the system - the process went very smoothly and the system seems well made and straightforward to work with from what I’ve seen so far. Delivery was about 3 weeks from what I recall. Pricing was more than acceptable in my opinion - at the lower end of what I was expecting to spend although that was based on retail prices of other systems’ replacement motors and parts that I’d been able to find. Documentation was very good although I did end up needing to scrap the first down tube as I drilled holes for the external battery mount from the docs and not doing an actual test fit before drilling (measure twice, cut once - lesson learned … again).
What attracted me to the Freeflow system is the relatively low profile and mid-power of the system. I own a Giant Fathom E+1 Pro (2020 model) with the Yamaha based full-fat motor. While I always come back from riding that with a grin on my face, I find the geometry to be very old-fashioned. I’ve always had trouble getting a good fit with commercial bikes - I either end up with good inside-leg clearance but short reach or vice-versa. I also find the motor is more than I actually want and the whole bike has been designed around supporting that, so over-engineered and heavy with a big, expensive battery and super-long chainstays - to stop you putting it in Turbo mode, going a-over-t, and then suing them to compensate for your own stupidity, I presume. I’m a lighter rider and have a fluid riding style which doesn’t punish bikes as much as the imagined 16-stone graceless bike park gorilla who manufacturers seem to be designing for these days 
so I don’t enjoy riding (or lifting over gates) all that extra weight.
I’m aiming to build something a bit closer to an acoustic bike than an electric one, with assistance when I need it but which feels like riding a regular bike as much as possible, and Freeflow appears to tick the appropriate boxes for that objective. For bonus points, Dave Hemming is their point man and, if you’re my age and were around in the early days of the UK mountain biking scene, that’ll mean something 