I'm not one to talk much about speculation and things yet to be released but AppleInsider has some compelling information regarding the ultra-portable MacBook we have all been hearing about. It won't feature a 12.1-inch LCD but will use a larger ultra-thin 13-inch LED-backlit display. Like other ultra-portable notebooks, it won't have an optical drive but the inclusion of onboard NAND flash "for faster application launching and boot times" and integrated iSight makes up for it. A MagSafe power connection and 802.11n wireless capabilities round out the package.
My biggest concern is whether Apple will market this notebook as a part of the MacBook or a MacBook Pro line. Naturally, it would seem like this would remain in the MacBook line since there is only one MacBook form factor at the moment compared to the two within the MacBook Pro line. Also the MacBook and MacBook Pro lines are oriented in a kind of "smallest to largest" format: 13-inch in the MacBook line and 15, 17-inch in the MacBook Pro line.
However, even with that knowledge I hope this cutting-edge ultra-portable makes it into the MacBook Pro line with a sleek metal body rather than (discoloring) plastic.
Another thing to analyze is whether or not the 13-inch ultra-thin display will have the resolution capabilities of the 13-inch display used in the regular MacBooks (capable of 1280x800 resolution). With ultra-portable notebooks, screen resolution isn't something people pay much attention to. For example, the 12-inch PowerBook G4 of yesteryear was among the most popular Apple products regardless of the lackluster 1024x768 resolution. Of course, it would definitely be nice to have a small laptop with incredible resolution.