I agree with oosik; the straighter (or more level) the shaft. the less strain on the U-joints.  I also agree with s219 that "on the ground" is more stable and puts less strain on the 3 point hitch.  When I used a borrowed Wally BX42 that had a low input shaft height so that the angle from my PTO was excessive, I used steel strapping to band a couple of short timbers (6x8's I think) to the skids.  That worked fine except that everything I put in the hopper had to be lifted the extra height.  The Salsco 6" 
chipper I ended up buying had a much larger flywheel that gave a better PTO shaft angle.  The Salsco also had a lower hopper bottom lip height than the comparable Wally.  I suppose the trade-off is how well gravity feeds on the different slopes of the chutes, but I find a 5/16" gap and sharp blades feed as aggressively as I want.
The price you reported should go a long way to quiet any small dissatisfactions you have with your Wally.