I want to replace my 2007 MBP with a MacBook Air, so I'm keen to see new model. I was disappointed when Apple didn't update the Air this week. However, I can think of a big technical reason to delay the update: the power efficiency of Intel's current 32nm Arrandale CPUs. If we consider the current Air, it uses 1.86 GHz (SL9400) or 2.13 GHz (SL9600) Core 2 Duos with 6 MB on-chip L2 cache. Both these CPUs are built on a 45nm process and have a TDP (thermal design power) of 17W. There are no faster Core 2 CPUs available at this TDP. If we look at the new Arrandale CPUs, the fastest CPU available with a similar TDP is the 18W Core i7-640UM, which runs at only 1.2 GHz. Admittedly this includes graphics, but if Apple stuck with Intel's integrated graphics, performance would be worse than the existing GeForce 9400. If we couple this with the much lower clock speed of the Arrandale CPU (1.2 GHz) compared with the existing Core 2 CPU (2.13 GHz) I think it's clear such an upgrade wouldn't be an improvement. The Arrandale does have hyperthreading and Turbo Boost, but that isn't enough to compensate for its huge clock speed disadvantage. In summary an Air built with current Arrandale CPUs would either be slower or more power hungry than the existing one. So there is no good reason to release a new Air at this time: yes 4GB of ram and larger SSDs would be nice, but Apple will save them for a proper revision. What happened to the hope part you ask? The bad news is that Intel's current 32nm process isn't yet very efficient, the good news is there is plenty of scope for improvement. To quote Anandtech: "...we see that idle power for Intel's 32nm part isn't very good. It's actually worse than the 45nm Lynnfield platform from earlier this year. Intel confirmed that there is a lot of optimization that has to happen with Arrandale. It looks like there are some silicon level tweaks that are on the roadmap to be implemented but we won't see them until the middle of 2010." (Arrandale review at Anandtech). Apple will still need to decide what to do about graphics, but having a faster CPU with good power consumption would be a big step forward. There is always the possibility Apple could discontinue the Air, but I'm choosing to be optimistic. I think we'll see a significant update to the Air this summer.