Just purchased this car as a replacement for our Honda Odyssey, which we thought was way too large for our family of 4. Fantastic build quality, fantastic engine, nice and high quality interior. The price for the nav is high, but it includes a lot of other goodies such as the HID lights, which are worth the extra expense. The price can exceed $45K quickly, but the RX 350 is one of the better deals out there. Great car for general use, but probably too small for an extended cross-country trip - the trunk and general passenger area are just too small.
Engine, build quality, size for getting around town, dealership experience: educate yourself before buying, shop around and buying this thing should be fun (except writing the check, of course).
The nav could be easier to use, way too many options, the speech recognition is painful to use; more legroom, roomier trunk. Rear view camera needs to be improved, now it's nearly useless - you can't estimate distances with it! And gas mileage! We have a tough time getting this thing above 16 MPG!