Opinions, concerns, and whatnot about these new machines would be worthwhile to hear. I've been waiting for these things to finally come out, and it seems that the iBook line may not be too far behind (and thus, my first Mac purchase in half a decade).
I have some concerns with Apple's play method here. This new "MacBook" (hate the name.) is quite the professional-orientated laptop. Holding onto many of the features of the higher-end G4 PowerBooks, and brand new X1800 ATI graphics (Even on the PC-side, this is a screamer of a chipset). Unfortunately, their pro products, their video editing applications, not to mention the applications of others are not yet in Universal Binary format, or even native x86 binaries yet. This is a problem for individauls who want to use these Macs for high-performance work, and have to settle for emulation until their mostly-killer apps are ported. This would push potential buyers either to another market or down to the G4 PowerBooks. However, if Apple can pull off at least Universal binaries of their apps, and perhaps rally other developers to follow suit (they've been doing it like crazy on the ADC newsletters) by the time these things ship, it looks like all lights would be green then. The iMac concerns me to a lesser degree. Since the OS has been ported natively to the Yonah's they're based on, the average consumer for whom the iMac is targeted at wouldn't be concerned with such packages. Gamers may even be pleased by the bump in graphics there as well, but of course, their games have to be ported again.
Many of us have already delt with these problems before, back when Apple was moving from 680x0's to the PowerPC architecture. History apparently has come to repeat themselves. I'm wondering how Classic is going to be supported at this point in time, Rosetta may not cover emulating 9.2.2 and even further back, classic 68k apps. Granted, everyone should have moved up by now, but legacy is always a good thing to know you can rely on.
I feel though, this is a good move for Apple in the end. They're increasing performance and battery life in their laptops, and also desktops. They're also pushing breaking-technology as well which no one else in the PC industry even has their hands on yet, outside of a few laptop dealers, but even those machines were engineering samples. I do not believe this will help or hurt software development any, seeing as how most high-level language-based code needs only be tweaked to play nice with X, and you're good to go (I still feel Apple needs to work on XCode more). I like the idea of the power connector, and I know first-hand how socket-based AC adaptors can be at times, the tips wearing out, and people tripping over them ("Flying PowerBook Syndrome"). A nice feature, but a small one, nothing too remarkable, but welcome all the same. However, they need to fix that name, "MacBook" sounds... childish.
Then again, with these Intel Duo cores (Intel, you too! These names are horrible!), they can't exactly call it "PowerBook Duo", now can they? ;p