The Arrandale processor is closely related to the desktop Clarkdale processor; both use dual-core dies based on the 32 nm Westmere version of the Nehalem microarchitecture and have integrated Graphics as well as PCI Express and DMI links [W].
Arrandale is going to deliver the single largest performance improvement we've seen from a new mobile processor in years. Hyper-Threading brings the many of the benefits of having a quad-core processor without the added power consumption. Turbo is also extremely useful in mobile since it's one of the most TDP-constrained environments you can imagine.
SYSMark 2007 shows an overall performance gain of almost 20% on a 2.53GHz Core i5-540M vs. a 2.53GHz Core 2 Duo P8700.
Video encoding performance gets a huge improvement as well. In their x264 HD 3.03 encoding test AnandTech found that performance improved 26% and 46% in the first and second encoding passes respectively.
A World of Warcraft test running at 800 x 600 at the lowest quality settings showed an improvement of 129% leading the reviewer to comment that the Arrandale's integrated graphics may actually be playable.
Battery life doesn't improve with this processor; however, a second version is expected later this year which will have better power characteristics.
Hit the link below for even more benchmarks and a detailed review of the processor.