This bike was by no means cheap, but it is packed with features. S604 offers a really solid and well thought-out bike for the money. As the title says, I've ridden over 1500 miles on this Rook in less than 9 months. It has not been entirely problem free, but the two problems I had were relatively minor and really not the fault of S604, but they were nevertheless sorted out with help from Mitchel and my local bike shop. I have the 21Ah battery, NCX seatpost, and a few other accessories I have added myself.
I usually keep the PAS set to 3-5, because don't like to pedal too hard (hence reason for the ebike!) With the upgraded 21Ah battery, my range is realistically close to 40miles on my moderately hilly mixed suburban and rural routes. YMMV, of course.
The Panaracer moped tires that came with it have been good. Decent traction and no flats so far, but I've probably been lucky. I do a lot of riding on shoulders which means I drive over broken glass, bits of wire, etc. I do recommend you practice how to change a flat before riding. I had to learn for a repair I did in my garage and with the rear hub motor + wires + spacers, etc, it would not be trivial to repair a flat on the side of the road even if you've done it before.
In all, I have very few complains. I likely will also be in the market for a more powerful mid-drive fat bike soon and I'd definitely consider Surface604 if they had an offering in this niche.
If you're on the fence, my advice is jump right in with Surface604. The time you spend researching it could be time out on the road riding your new ebike!