Ah hell, 1200 hours is like a car with 36,000 miles, assuming 30 mph average. I'd consider anything under 1500 to be low hours. Over 5000 starts to be high hours in my opinion.
Definitely want to check for a few things over a few hundred hours though. Mostly, I'd want to check to see that it isn't still wearing the factory filters (engine oil, hydro oil, and HST filter). The majority of tractors come with filters painted the same color as the body, so it's easy to see if they're original. I'd also want to make sure there's no leaks, and check the loader to make sure it's not sloppy. I'd rather own a tractor that mowed for 2000 hours than one that got the crap beat out of the loader for 800 hours. Also, you should be able to put a hydro tractor in high range and push up against an immovable object and get the pump to go into relief. Otherwise, the pump might be getting weak.