iBook G4 12" 1GHz, bought in September 2004, had to have a logic board replacement after the infamous 18 months.
Alu iMac C2D 20" 2GHz, bought in October 2007. No repairs yet.
white MacBook C2D 2.4GHz, bought in August 2008. No repairs yet, might bring it in for replacing/repairing the top case.
Unibody MacBook Pro 15" C2D 2.53GHz, bought in December 2008. No repairs, but got stolen in June 2009. May the next owner has less luck.
Unibody MacBook Pro 17" C2D 2.8GHz, bought in June, two days after my 15MBP left me for no reasons. Works fine.
In the end I have to say the iBook, even though it had to get repaired, was the best Apple machine I ever had in terms of stability and durability of the notebook and Mac OS X it has on it.
The Intel machines come close, but they got more quirks than the PPC ones I have worked with.
Gaining market share might be not as good as we might think it is, as it introduces more weak points in Apple's production.