Hi,
I bought a 59 reg SE-I from a private seller back in July and I am well pleased with it. It has done 25k mls and the only things I really wanted to make sure of were verification of the mileage, Lexus service record, previous accident damage and general condition (no dings, decent tyres etc).
I like to think you can take reliability for granted with Lexus and it is good to have a bit of warranty left although if you are looking at a 60k-er I guess there are other replacement items to be taken into account.
Other than that I always try and get as much spec for as little as possible. Mine came with rear DVD's, roof rails, rubber bumper protectors and a full set of rubber floor mats. Having said that the SE-L comes with a bit more spec but I could not find one within the budget.
Overall a great car and an improvement over the much earlier '05 RX 300 I had a few years ago.
Only word of warning is the fuel consumption - mine has settled down to about 30mpg which is not bad but nowhere near the claimed 44mpg!!
Happy hunting!