Nah they aren't that much of a good deal. Alot of dealers last year had brand new TBi's in Turismo Sport trim going for a mere £13k now that was a bargain. The trouble is the spec isn't up to everyones taste and the TBi isn't all that great either!!
You pay for what you get although personally, I'd have a Turismo over a Lusso anyday providing it had Blue and Me!.
I posted on these a while back as I live just round the corner and can't miss 20 odd 159's sat shoulder to shoulder as I drive by. The big diffeence does seme to be these are full fat models with all the toys, though as you rightly say no TI spec. I thought they were cheap when i saw them though they dont seem to have sold many so far