One of the benchmarking tools I use for testing and evaluating Macs is Geekbench from Primate Labs. Primate Labs has just put together a collection of benchmarks for the new 2011 iMac, using the results of benchmarks submitted by Geekbench users. The results vary, depending on specific iMac configurations, but it seems there is at least a 25% increase in raw processor and memory performance due to the new Sandy Bridge processor architecture in the new iMacs.
Courtesy of Apple
The iMac Benchmarks (Early 2011) lists the 2011 version of the 27-inch iMac with 3.4 GHz Intel Core i7 as the best performer, followed by last year's 2.93 GHz Intel Core i7.
Although the performance gains appear to be modest when compared to the previous generation, they are much more compelling for anyone with an iMac that is two generations or more old.
So, if performance is a key factor in deciding whether to upgrade, those of you with iMacs based on Intel's older Core 2 Duo should be very pleased with the 2011 iMac's performance.