Until today, Apple’s three laptop lines used different display connectors. The MacBook used mini-DVI, the MacBook Air used micro-DVI, and the MacBook Pro used vanilla DVI. I thought Apple might standardize on a single display connector, perhaps micro-DVI.
I was partially correct. Today’s updated versions of the MacBook, MacBook Air, and MacBook Pro do all use the same display connector, but it’s mini-DisplayPort, not micro-DVI.
Apple needed another laptop display connector like a moose needs a hat rack, but mini-DisplayPort does have some advantages. For one, the connector is small—about 60% the size of a standard USB-A connector. (See comparison image, above.) It has a 1 Mbps bi-directional (half-duplex) auxiliary channel that could be used to handle webcam or other peripheral data. It can also drive resolutions above 1920×1200, which dual-link DVI can handle but single-link DVI variants can not. Perhaps the connector will mate with the socket more securely than mini-DVI does, but this is yet to be determined. (Latching is a feature of standard DisplayPort connectors, but so far as I can tell Apple created mini-DisplayPort on its own. It is unclear if mini-DisplayPort connectors latch. [update: They don’t.])
The downside? Mini-DisplayPort is presumably signal-compatible with standard DisplayPort, which “is the future” but hasn’t really caught on yet. This will likely be a win in the long term, but it’s not signal-compatible with DVI or HMDI (nor VGA, for that matter). DisplayPort implementations are permitted to pass DVI-compatible signals through the connector, and presumably this is what Apple has done, at least for single-link DVI.
Apple’s $29 Mini DisplayPort to DVI Adapter supports single-link DVI. To exceed 1920×1200 requires the Mini DisplayPort to Dual-Link DVI Adapter, priced at a whopping $99. Presumably the dual-link adapter has circuitry that actually converts the DisplayPort signals, which is why it requires USB power. (There is also a $29 Mini DisplayPort to VGA Adapter.)