I've had a Power Pro ever since they were first introduced. It came as a kit, so I assembled it all into the old headstock and offset some of the cost by selling the old motor, speed reducer and speed increaser. I've only had one issue with it, which a tweak of the firmware has cured. I believe that there was a 2nd issue of firmware for the newer Power Pros and this cures my problem. What happened was that the set screws on the power coupler hub for the bandsaw would come loose, despite heavy tightening and application of Loctite. The cause was over and undershoot of the speed controller at high frequency, which resonated the set screws on the coupler. Wes at Shopsmith called me by phone and walked me through a procedure to make an adjustment and it's been fine ever since.
I have had no problem with sawdust in the headstock, despite there being a small open hole where the old power cord entered the lower casing. In fact I had the covers off 2 days ago to inspect the headstock lock (first time in many years) and there was minimal ingress of dirt or dust. What there was, I removed with compressed air.
There is a procedure for belt tensioning which is easy to follow, but shouldn't be necessary for a factory-built unit. You would know if the belts were out of adjustment, because the headstock would get noisy and if you adjust immediately, no damage should occur. I've not had to do that since my initial setup.
The belts are very tight and run hot. My garage mechanic friend assures me that this is quite normal on modern automobiles, so there is no issue with the Power Pro.
The only maintenance I've found necessary on the headstock is to remove the quill every so often, clean off any crap and wax it. I also removed the headstock locking mechanism, re-dressed the wedges and applied some graphite to the screw threads.
I fitted the upgraded castors quite a few years ago and they're a brilliant improvement for my rough concrete floor. Unless you were wheeling the unit around all day long, day after day, I doubt you would damage the castors, even with the extra weight of the Power Pro.
There are two major advantages to the Power Pro - full torque at all speeds, which you don't get from a conventional motor with adjustable belts. I've not managed to make mine bog down yet and I do push it too hard sometimes!
With the shaper attachments, its possible to reverse the cutters and feed in the opposite direction to 'normal' and you simply reverse the motor with a press of a button.
There is one small and rather obscure disadvantage with the Power Pro, which most folks would never know about. As a Radio Ham, I am very sensitive about man-made RF 'noise'! The Power Pro controller throws out a lot of that, despite being enclosed by metal. It's not the motor because it does this when it's at standby. Fortunately there are no other Radio Hams near me to be affected and I don't go 'on-the-air' when I'm woodworking, so no significant effect on me either.