As far as the change to intel goes, it's a lot of hype. The intel processors are faster the g5 on certain benchmarks, just like the g5's were faster than the best intel chips on certain benchmarks. They just pick the benchmarks that show them off the best and use those.
Apple simply couldn't get IBM to give them a low cost low power G5 for laptops because of the relatively small order quantity so they went with off the shelf intel chips. More profit for them as well. IBM didn't care because they captured the CPU orders for all 3 of the new game consoles including M$'s Xbox 360
Battery life on intel based laptops have always been dismal compared to the ibooks with g4's in them. The g4 (made by Motorola) is an extremely efficient chip in terms of power consumption. I'm sure the battery claims on the new MacBooks are inflated. They probably have bigger, heavier batteries as well.
That's not really all it was. Market share and order quantity were one part of the equation, I'm sure, but... IBM couldn't deliver a low-heat, low-power version of the 970 because of leakage, not just because of market share. There were also some serious yield issues at first, and the cooling required for the higher-end G5's was problematic (this comes from someone in an office with 4 liquid cooled PowerMac G5's -- two of which have had the CPU units replaced twice each for cooling problems). All for much the same reason Intel couldn't push the
Netbust Netburst architechture into a laptop form-factor efficiently and eventually had to abandon it for the P3/Pentium M/Yonah architechture (not to mention that they were and are getting slapped by AMD's performance).
There's also a huge amount of speculation that
Apple wanted Intel's PDA-architechture processors (Xscale) for some new as-yet-unannounced iPDA product. We shall see...
The G4-based PowerBook's battery life was certainly superior to anything Intel has now, but there were other huge problems with those systems too. They were choking on an incredibly antiquated bus (bandwidth starved), so they really couldn't effectively use any of the clockspeed increases that Motorola did manage to squeeze out of them. Basically the same problem Intel had with the Pentium 3 just near the end of it's life. Apple/Motorola/IBM just didn't have a genius Israli team to produce the G4-M for them like Intel did (and there lies the order quantity issue). The problem really was that ALL of the major chip manufacturers, excepting AMD, went down the "slay everything to the almighty GHz" route and didn't consider power consumption and transistor leakage to be the problem they ultimately turned out to be. The G4 was a beautiful processor system for it's time, but it was still running on a 133MHz bus....
Intel had economies of scale, the Xscale processor, and the ability to deliver in REAL volume if Apple's sales really take off (
as they appear to be).
Oh, and as far as dual-booting?
Apple has said repeatedly that they will not stand in the way of booting Windows on a Mac. Booting OSX on a commodity PC will be more difficult, and Apple will try to prevent that (probably, though who knows), but I would be surprised if it doesn't eventually happen. They won't like it, and it certainly won't be easy, but...
Microsoft didn't think you'd be able to boot Linux on the XBox either. Hackers will hack, and if they make it illegal, they'll just do it in China.