I've an 07 IS250. I've only had it 6 months, but have 15K km on the clock so almost your 10k miles ;)
I'm very happy with my car. Only two disappointments.
1. Despite the 07 model, there are still rattles. In fairness my dealer solved almost all of them. One they failed to solve, and another one or two minor ones have developed in other areas since. They are less than I've been used to in other cars, but it's a matter of expectation, and I didn't expect ANY rattles, minor or otherwise, in my Lexus.
2. I left it in for it's first service recently. Lexus kindly offered to touch up some paint marks (none of which were my fault!) free of charge. They did this, less than perfect, but since it was foc I've no complaints. However they did return it with a NEW scrap on the passenger door handle. Too small to complain and make an issue of. I've always dreaded leading a car into a garage as they always seem to suffer from some sort of garage rash, but again it's one of expectation, and I would have expected more from a premium marke.
Other than the minor scrape in the garage, I've been very happy with the service I've received from the dealer, from demo to 1st service.
On the up side, I love the power of my IS250. I've no problem with the 27mpg as it's more than I was expecting (again expectations are what counts!) and I'm constantly getting compliments on the car.
This is my first Lexus, and I would certainly consider another one, though I'm not so sure about the styling of the other models! I just wish they could produce a car that was rattle free, first time, and stayed rattle free........I'd happily pay them more if they could guarantee this.
I would never consider a diesel Lexus though, having had a diesel IS as a courtesy car.....the diesel and the petrol and worlds apart in my view, and the refinement of the petrol is definately worth the extra running costs.
Colm