Currently I have a Yamaha PW-SE mid drive gravel bike and a Tongsheng TSDZ2 mid drive on my wife's bike. From what I read mid drives, in general, seem to be reliable and long lasting. But what happens when one breaks down (there are plenty of anecdotes on this forum) ? The motor alone can cost $1000, not including any peripherals or labor for installation, parts might not be available for repair or be too complex for DIY or excessively expensive to have professional repairs done. Down the line motor design can change which can make the bike frame useless if the mounting points or other form factors don't fit. I have regular pedal bikes that are decades old but standard generic parts are still available, it seems unlikely that the same will be true for mid drive frames which are designed for specific proprietary motors as well as batteries. One could pay thousands for a nice mid drive ebike and in not too many years end up with a unusable bike. I like my Yamaha powered gravel bike a lot but most probably wouldn't have bought it (even at the greatly discounted price I paid) if I had been aware of the TS mid drive. I'm just a recreational road/gravel path rider but the TS seems as powerful and refined as the Yamaha, cost less than $650 including peripherals and the battery and can be easily and quickly removed from a bike to return it to it's regular analog state. There are some potential fitment issues on some frames, chainline and chainring considerations etc. but in the long run it, or similar add on kits, could be a better solution than much more expensive bikes with frames made for proprietary motors. Especially for purely recreational road and path riders - which probably covers the majority of ebike riders.