It feels a lot like Apple have hit their stride in terms of their industry position. Market share is way up, and with it hits standard consumer expectation. For Apple, that basically means they have to scale back the big, game-changing hardware changes to some extent and act more like a traditional OEM to stabilise any large changes in consumer movement. Knocking specs up to match current tech as opposed to large changes in hardware, testing designs with single Rev A hardware releases then standardising the look across the line if it takes off etc.
The NetBook is an awkward product for them at the moment because of where it would sit in their existing product line-up. One thing the big OEM's currently aren't afraid to do is to use a diverse range of hardware across their systems - Dell for instance will go up as far as Core 2 Quads/Xeons in their top end stuff, right down to Atom's and Celeron's at the low-end. This experience allows them to slap pretty much any random cheap hardware in their NetBook's without fear. Not so for Apple - they extensively test and select a particular CPU/GPU line for their systems, and pretty much stick to it across all products. NetBook's are quite a price-driven product; they're importance is in their low-cost, which means for Apple to compete (even though they'd still likely be Â£100-Â£200 more expensive) and retain their oh-so-important profit margins they'd have to look at using a completely revised spec in terms of hardware, which is gonna take some R&D time and spending to get the balance right. I think for the time being, they'd be looking at their iPhone as their NetBook competitor and developing that to compete.