Placing the new MacBook and the side by side, there are many small physical differences. Because of its unibody construction (in this case, a piece of polycarbonate instead of aluminum), the new MacBook has no grayish surface grafted atop the frame. The result is a consistent white color, and a smoother surface without the sharp edges of the earlier generation. It also means a lot fewer screws--the older MacBook had two screws on each side, plus four on the back to the sides of the display hinge. This model does away with all of those screws.
A big difference is that the new MacBook now has a glass Multi-Touch trackpad with gesture support. The trackpad is larger than the combined pad-and-button area on the old model. The smooth glass feels nicer than the older trackpad, but it does take getting used to if you've been using the previous design.
The new MacBook also has a round iSight hole (as opposed to a rounded square) with only a status light to its right. (The microphone has moved to the upper left corner of the keyboard area.) The power button is smaller, and the keyboard keys feel more solid and are a bit quieter than before.
The 13.3-inch display offers the same 1280-by-800-pixel resolution as before, but the new MacBook uses LED backlighting on its display (just like the 13-inch MacBook Pro). The difference is a notably brighter output, although when viewed next to each other, the new MacBook shows a significant yellow color shift when changing your horizontal viewing angle (the previous model simply got more washed out).
The screen back has a slight taper (like the MacBook Air) that gives it a thinner appearance than the constant thickness of yore.
Overall, the new MacBook is slightly wider and deeper than its predecessor, although it shaves 0.3 pounds from the total weight. Oddly, when I first picked it up I thought it was heavier than the older MacBook--a sensation I attribute to a different distribution of weight because of the thinner display in the new model.
On the front edge, the sleep status indicator is longer and narrower than before, and conspicuously absent is the infrared (IR) port that used to sit to the right of it. Without an IR port, you can't use the (or the older remote, for that matter). I don't consider this a huge loss, since I never used an Apple Remote to control my MacBook. (In fact, I've been frequently annoyed when I used the remote to control my Apple TV and it threw the MacBook on the couch into Front Row at the same time.)
Speaking of ports, there are also some changes to the array of ports on the side of the MacBook. To get it out of the way--no, there isn't a FireWire point on this MacBook. The white MacBook had been the only 13-inch laptop from Apple with a FireWire port (until the ) and now it's gone from the low end. If you need a small laptop with a FireWire port, this MacBook isn't for you (for an extra $200 you can move up to a similarly-sized MacBook Pro, which includes a FireWire 800 port as well as an SD slot). The display connection is now Mini DisplayPort (previously there was a mini-DVI connector), and Apple is using a single audio port for analog/digital output as well as line in. (The Sound preference pane has a Use Audio Port For pop-up menu from which you can choose either Sound Output or Sound Input.) The sound port supports the Apple Stereo Headset with microphone. The other ports are gigabit Ethernet, MagSafe power, two USB 2.0, and a Kensington lock slot. As before, the other side features an 8x slot-loading double-layer SuperDrive.
The back/bottom of the MacBook no longer has any padded feet--mostly because the entire back surface is one giant rubberized foot. It's secured by eight Philips screws. You won't find a battery compartment on the back either, since this is the first white MacBook with a built-in battery. Apple says the custom battery--which saves space in the notebook's design--offers up to seven hours of runtime and up to 1000 charge cycles. As with Apple's other unibody laptops, the battery is not user replaceable, and there's no charge status indicator either.
One thing I haven't had a chance to do yet is take the rubber back panel off to see if hard drive swapping is as easy as in the past.
The latest MacBook stills uses an Intel Core 2 Duo processor, but bumps the speed from 2.13GHz to 2.26GHz (both have 3MB of shared L2 cache). And although the MacBook maintains the same 1066MHz frontside bus, the new model supports 1066MHz DDR3 RAM as opposed to 800MHz DDR2 RAM (4GB is still the supported RAM limit). The MacBook also retains its 802.11n and Bluetooth 2.1 wireless networking.
Graphics-wise, the new MacBook uses the same Nvidia GeForce 9400M graphics processor that shares 256MB of RAM with main memory (although, as I mentioned, the system RAM is faster). That processor still lets you mirror or extend your desktop to a second display at up to 2560 by 1600 resolution at millions of colors. You won't find any of the Mini DisplayPort adapters you'll need to connect to an external display, however, in the box. Each is sold separately by Apple.