Get him to show you how to determine, from the operator's seat, that the FEL bucket is level. The bucket level indicator on my
L4300's FEL isn't much help.
Make sure you can smoothly control FEL/bucket movement in all directions using the joystick and that the arms latch into 'float'. Check that the hydraulic lines are well secured and routed and that nothing looks likes it's being stretched at the motion extremes. You might want to get the salesman to demo an FEL removal/replacement and also a bucket remove/replace if you have quick attach.
Operate all the controls, make sure the 4WD and the differential lock engage and disengage smoothly. If possible hook up a load to the PTO (maybe a bushhog....been thinking 'bout a new one, right? /forums/images/graemlins/wink.gif) and engage the PTO, vary engine speed, and disengage. Have the salesman show you how to feather the PTO engagement at slow speed to bring the implement online smoothly. If you've gotten this far, check that the 3-pt hitch smoothly raises and lowers the bushhog.
Try all the gears/ranges in the transmission. You'll hear some noise in the High range...that's normal. Try to run it at road speed for 100 yards or so...see if the front wheels shimmy or chuck and see how the steering feels; it shouldn't feel skittish. At slow speed, take the steering through its full range, left-to-right, and look for any sign of binding.
Check each brake independently and see that they engage at about the same pedal level. Make sure you understand how to engage and disengage the parking brake latch.
Look for anything that might be loose. Look for some grease at the zerk fitting points
Also check the electrical. Make sure all the lights work and that the light switch has a solid feel and works the same way every time. Make sure the light wiring under the fenders is well secured and in no danger of catching a tire cleat. Might want to see if the wiring under the hood is well secured as well.
While you're under the hood, check fluid level in the radiator overflow bottle...make sure it's at the full mark. Get your salesman to demonstrate how to remove, clean and replace the screen in front of the radiator....you'll be doing it alot if you bushhog so give it a try yourself too. Make sure you know how to check all the fluids.
That's about all I can think of for now....hope it helps.
Bob