Apple's brand new iMacs, while having the expected spec bump in terms of raw processor power and graphics capabilities, were about as conservative as you can get  in terms of adjusting the actual look and feel. The only real excitement seemed to be that they now had a Thunderbolt port or two on the back to link up super-speedy peripherals and multiple displays. But now it seems that inside their shiny metal guts, the new iMacs have a handful of carefully hidden secrets.
Mixed-mode solid-state/hard-disk drives
Among the semiconductor components dotted on the new iMac's motherboard hides Intel's BD82Z86  Platform Controller Hub. If that doesn't immediately get your spine tingling, then you're forgiven--it's a seemingly esoteric bit of hardware. Except...Intel's not officially releasing it for about a week, which suggests Apple has once again snagged early access to hardware from Intel (those chip foundry rumors sound a little more positive now).
But better yet, the Z86 uses Intel's "Smart Response Technology" which utilizes a smaller-capacity SSD as a "high-speed cache" for a larger traditional hard drive. Some slightly flexible language on Apple's iMac specs page about buy-to-order SSD-equipped iMacs even hints that at some point Apple may enable the SSD and HDD to play together as a single rapid-cached drive inside your Mac. And that's just one step before Macs go 100% SSD.
Changeable graphics units
iMacs have always been tricky beasts to repair, let alone upgrade, thanks to the extremely crammed-in nature of a design that seems to optimize every square inch inside the slender case. If your graphics card in older iMacs went kaput, then you were looking at a very difficult and potentially expensive repair. But now iFixit has found, during its tear-down  of the new machines, that Apple has made it much easier to swap out the AMD GPU in case of damage. In fact, it's just about possible that hackers and tweakers could upgrade the GPU themselves--all it takes is a little smart dismantling, and removal of the bulky GPU heatsink.
Back-lit wireless keyboards
This one's not so exciting, or even definite, but it is interesting: The new iMacs ship with a setting in their OS that corresponds to a back-lit keyboard . The machines also have an ambient light sensor--a new addition--next to their webcam, in a configuration that only MacBook Pros have now. Since iMacs, by definition, lack a built-in keyboard, this is being taken as a hint that Apple has been working on an upgrade to its popular slim wired (and possibly even wireless) keyboards that includes backlit keys.
Three tiny tweaks, then... hinting that while Apple may be taking the slow and sensible route  to updating its hardware in 2011, it's still taking the opportunity to refine and improve its offerings.