I got an RX300SE last month, my thoughts so far;
Paint work, completely immaculate on delivery, I inspected it very closely after reading about another owners issue. Now have one stone chip after a 600 mile trip to hull and back, BUT, this is common on modern cars with their water based paints. Don't think it is any worse than my last BMW which got chips after motorway journeys also...
Wheels, if they corrode get them swapped at service time, not something worth doing a long trip over. Not a big deal as long as in warranty... heard similar issues on mazda alloys (father-in-law on second set on his Mazda 6). I also had a set of BMW ones that need replaced through corrosion...think it is a common issue but not worth not getting a car because of it.
MPG..26-27 on the inital trip to Hull, about 20 mpg around town.
Must say I love the car, never looked at the Nissan as I was wanting more luxury than anything else this time round...which the RX is very good at. certainly no sports car though..
I 'd say buy one.. but I am biased as I bought one and love it..