well its not like you will be able to install tiger on your cheapo PEE CEE yet. Probably, it'll be customized x86... and yeah why not? Pentium M is a pretty solid li'l thing... and as portable sales are exceeding the desktop sales... apple HAD to shift to something faster since g5 was too hot for a lappie...
Apple did not ditch IBM, IBM ditched Apple... they promised 3ghz two years ago and haven't delivered yet... Again, the $999 developer Powermac p4 3.6 ghz will be way way slower than the dual g5 2.0 ghz leave alone the dual 2.7 ghz which prolly is even faster than amd x2...
Update: It seems as if ibook, powerbook and mac mini will have pentium M and imac, powermac will have Pentium D though i seriously doubt the performance of a D against that of a dual g5