If you still have the MX8, you can also check to see if they make different tires/treads that are possibly better suited to fiberglass. Also, search here for members who may have the MX8 and discuss any issues you have directly with them. If you can get it to work acceptably, no use spending $$$ on a new cleaner
As pooldv stated, many members love their robots. They are a bit pricier though. Have a read through some of the threads in the Pool Cleaners forum.