It's an excellent value line tractor, made for a yard as you describe. If you desire to mow a larger area or an area with more demanding hills, there are other JD models that may provide a longer service life. In the $1,999 price range, there is no other tractor in the marketplace that can provide the power (22hp), efficiency (48" mower), or reliability and comfort (JD staples) of that model. Check out the May 2010 Consumer Reports. It's a top pick, and has vastly better reliability than any other make tractor.
In the $3,500 price range, JD offers the X300-Series of lawn tractors with similar horsepower and deck size that are designed for larger properties, harsher conditions, and more deluxe features. If you can spring for that, please give them a look as well.
Only downside I can see for the LA145 is the Tuff-Torq T40 trans. But as engine tech stated it should be alright for your property. But if you want to stay in the LA series You may want to look at a LA165 which still has a 48inch deck and has a Tuff-torq K46 trans which you will fined in the X300,X300R & X304AWS models.:thThumbsU
BTW Welcome to the Forum:MTF_wel:
The LA145 would be a fine choice for mowing duties on a flat yard of 3/4 of an acre. If you are considering doing more with the mower (snow, trailer, aerating, etc.) an upgrade might be a prudent choice.
I f you are just going to mow grass, than that is a fine mower and should last quite a while if you take care of it. If you are going to do a lot more with it, than you may want to go with the x series.