Apple today quietly updated their iMac line of desktop computers, adding faster fourth-generation Intel processors, improved GPUs, faster WiFi, and updated Flash storage. The update is the first major change to the iMac line since last year, when it was updated with a new, thinner design.
Apple is slowly updating its Mac lineup. The MacBook Air and iMac have now been updated to the Intel Haswell processor platform, while the Mac Mini and Mac Pro have yet to see any change. Expect those two to receive updates in the coming month or so, potentially alongside the launch of Mavericks, expected in October.
The Mac Pro is also due for an update, though that will almost certainly be released alongside Mavericks.