I wanted to change it out untill I replaced the knives and ran higher octane fuel. It really eats wood now so I am in no rush. The old rental owners rebuilt the head so it is pretty tight.
I deal mostly with soft woods, work just myself and a couple guys with a small chip truck; generally faster chipping is not going to be the best investment untill I get a bigger truck.
I highly recomend this machine. I was looking at a 97 BB90 86hp with 1400 hrs from westspur in bellingham washington for 12g. I was very concerned about the 37 horse wisconsin, but for 6g less... Don't shy away from the 37 horse, it is no worries, it damn near keeps up to a friends vermeer bc1000 with the usual brush debris.
My complaints of no big concern are; the space between the feed rollers and the disk can get packed up with small branches expecially when the knives are dulling. I keep a few sticks to last to push it through. It is heavy compared to the 6" vermeer I was using. This makes moving it around by hand almost a no go; I put my back out trying it by myself. Last, the panic bar does not seem like it would disengage the rollers if you were grabbed when feeding from the side; I just keep a hand on the panic bar. Anyrate all is well, just wish I was using it more this time of the year!