There's also focus. Apple has always focused on the consumer. At best, the "prosumer," which is a nice way to say a consumer with a bigger budget. They've never made the needs of larger businesses their priority -- even when they're doing the necessary work: for example, when they introduced things like Apple Remote Desktop, they talked about it in terms of school computer labs.

RIM is primarily focused on the business side. The tablet, in this form factor, can fit into a purse or (har har) folio pretty easily. It talks to the blackberry their customers will already have. It's a way to extend the platform with a bigger screen, for Word documents, spreadsheets, etc, without losing the point of their brand.

Apple -- and bless them for it -- pushes the bar up across the board for user interfaces, usable power (as far as I can remember, other smartphones as powerful as the iPhone had terrible battery life), stability (remember windows mobile, and garnett), and pure capability (HDR photos). But, they've chosen to focus their energies on an intentionally-narrow set of products. There's plenty of space in the market for them, Android, and RIM. Apple's got the core consumer experience down pat. Android's got the variety and hardware development pace. RIM's got messaging.

Maybe Meego too, but that's probably just my silly wishing ;-) Why don't more Linux-based smartphone platforms come with an X server? :-(