interesting post Des,always good to get some alternative views.
I have to admit to being a big Lexus fan and if I was thinking of getting another rag top(tin top) then the SC430 would be top of the list over the Boxster,S2000,Alfa Spideretc.
IMO your mechanic was right about Lexus reliability,Lexus have taken reliability to a level that most other manufacturers can only dream about.
BUT thats not the point when you buy a xf,to me you are buying those classic retro looks,that boat-tail back end must have been inspired by Bill Mitchell's '71 Buick Riviera,what more do you want?
Add to that a practical hatchback and it means you have a Sunday afternoon sports car that can also accomodate a big dog,essential for me.
As a daily driver,probably not, but thats what old Volvo estates are for, taking care of all the boring stuff.
As you will gather I'm looking forward to getting a xf but its still price and future depreciation driven so I wouldn't touch a late one, I think the early ones will be going for the proverbial song soon and then I will make someone an offer they can't refuse.
Be interested to know what you finally decide.