I'm pretty sure that this new MacBook is a pretty nice machine, in fact, i'm sure that in some ways it would blow away even my brand new 15" powerbook (November 2005 revision). But, for starters, i'm very happy with this machine and the new PowerBook, excuse me MacBook, (also, I agree with John Gruber in his MacWorld predictions, MacBook sounds like the Apple marketing team simply choked on coming up with a name for this) just seems like while the raw benchmarks look very good. Apple did this to us a few years ago, when the G5 debuted, their rhetoric at the time harkened back to the ads from some time ago, I can't seem to find them right now but the copy was something like this:

Apple computer would like to publicly apoligise for toasting the intel pentium processor

We were, at that time, led to believe that the PowerPC processor was the greatest thing since sliced bread. But, as we all now know, even apple had serious questions about the future of the PowerPC line even long before the introduction of the G5 chip.
So, Steve, forgive me if I don't accept at face value your claim of a 4x+ speed boost. Because, as we all know, statistics lie, I just wasn't sure *how* they were making these statistics lie, I know that they forged the G5 vs Xenon benchmarks. In fact Steve even tried to allay our fears about him doing it again, did anyone else notice the line about how "we used the best compiler from IBM and Intel on each system"? Well, back when the G5 was introduced Apple took a lot of heat over their benchmarks because a generic non-optimized compiler was used on the Intel system while a highly optimized compiler was used on the IBM G5. Statistics Lie.
Now, we find out how they did it this time.

In short, Apple used multiprocessor benchmarks to skew the performance advantage that its Intel-based machines enjoy compared to single-core PowerPC G4 and G5. Apple used the industry-standard SPEC suite components SPECint2000 and SPECfp2000, but here's the catch: Apple used SPECint_rate2000 and SPECfp_rate2000. Both tests spawn multiple parallel benchmark processes and are specifically intended for comparing multiprocessor systems. Single CPU, or single-core machines do positively lousy on SPEC*_rate2000 tests. That's predictable and universally understood. Add a second CPU or a second core and, as you would expect, SPEC*_rate2000 performance on any multiprocessor-optimized test skyrockets compared to a single-processor box.

That said, I think that they MacBook is a very nice machine, but the fact that i'm not that likely to see a much higher real-world preformance gain from the upgrade, and the fact that this machine is only a few months old lead me to say I will not upgrade, not now.
Now, I do love the new systems, the MagSafe connector is fantastic, I have had this issue pop up on my old powerbook, one time quite spectacularly. I was sitting in my dorm room, minding my own business when a guy from the campus IT department came around (which is an interesting story by itself) I was sitting in a chair with my feet up on my bed, my powerbook in my lap, my headphones on very loud, he had knocked and rang the bell, both on the outside door and the door to my room, but getting no response opened and came into both, I looked up seeing this rather imposing person in my room I promptly got startled so out of my wits that I promptly went flying off the chair, my powerbook cable getting tangled in my legs taking my powerbook with it. To make a long story short, the powerbook never sat flat on a table again :(. MagSafe could have saved me from that.
I like the 667MHz front side bus, that's double (didn't Steve say triple? more lies?) my 333MHz FSB.
Dropping FireWire 800 is a mistake and is going to alienate Apple's core.
I'm very unfamiliar with ExpressCard, is this backwards compatible with CardBus? Overall, I don't use the card slot on my powerbook, with everything built in (the way I want it) the only thing that I can imagine using it for is an EVDO modem, but since I work from home this is hard to justify :P.
SATA hard drives are nice.
The resolution on the new MacBook is actually *lower* than on my PowerBook, 1440×900 as opposed to 1440×960, that's a loss of 86,400 pixels, or 6.25%.
It weighs the same as my PowerBook, is marginally thinner though significantly larger in size, (5.61 square inches larger)
The big dissapointemt for me, and the only thing that could have convinced me to upgrade, is the ram limit of 2gb. I have 2gb in this powerbook and while it's, for sure, better than the 768mb I had in the old G4 12" I could never have too much.
I also haven't heard anything about power consumption or expected battery life, so i'm going to assume it's shorter, probably drastically shorter, than the G4 PowerBook. I recently took this powerbook to a post-holiday party at a family members house to watch movies on the long car ride there, I was able to use the powerbook both ways, about 2 hours each way, watching TV (off the hard drive, the optical drive obviously kills the battery) listening to iTunes and doing other sundry stuff. not too shabby. I am not willing to give this up.
I too, along with John Gruber, thought that MacMinis would be coming today, because they are the perfect low-cost developer machines. Apple could have, and should have, sold them along-side the regular PowerPC mac mini touting them as something for the developers, including what is probably the majority of developers that probably can't afford the exhorbanant prices for the ADC subscription required to have the privilege of purchasing a DevKit mac for $999. I think that the small-time developer, who wants to be able to test Intel compatiiblity would have been much happier with a $499 MacMini than with a $1200 iMac. Basically, i'm just not convinced that these Intel Macs are something that you are going to want to be using on a daily basis just yet, at least until more stuff is out as universal binaries.
I have at least four people, none of which have ever owned macs before, who asked for my advice over the holidays about which mac to buy. I told them to hold off, at least until after the Keynote. Two of them want Laptops and the other two want some kind of desktop solution. I'm most likely going to reccomend (I told them all to email me on Wednesday, after the keynote) G4 PowerBooks and G5 iMacs. Sorry Steve.