I had the 2009 X extreme with the PERM Motor and White Bros Forks. My opinion is based on a dirtbike background so take it for what's it worth.
Power: The power was never a problem for riding single track. The bike had an issue getting traction on rocky hills, it would bounce and spin alot. I assumed this was due to the lack of weight 150lbs.
Suspension: I tryed numerous times to dial in the fork and shock settings but could never find a better setting. The mountain bike components used air to adjust bottoming resistance which I didn't care for.
Brakes: I felt the brakes were too weak and not up to the task. Pads wore out quickly.
Handling: Light weight and the linear power delivery of the electric motor made for a fun time riding tight trails.
Battery Life: Max 2 hours of ride time with minimal full throttle..... mostly up /down trail riding on the side of the mountain. Usually around 1.5 hrs with some spirited riding. Ran the battery down a few times and pushed home to recharge. Battery later had a dead cell which was repaired under warranty.
Noted: The lack of engine braking made for a quick decent downhill and put stress on F/R brakes to control speed. Also when freewheeling, power wouldn't engage until motor rpm gets below throttle position.......ex. going downhill freewheeling and using full throttle to accelerate faster.......motor controller will disable power
This proved nerve racking when approaching a downhill tabletop jump and attempted to launch off jump face with power on. Power would hit suddenly almost causing a loop out and crash
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I did have fun riding this bike in different environments and the newer models addressed many of my complaints here.
Thx Pennjon