From the balanced notebook perspective, Arrandale is awesome. Battery life doesn't improve, but performance goes up tremendously. The end result is better performance for hopefully the same power consumption. If you're stuck with an aging laptop it's worth the wait. If you can wait even longer we expect to see a second rev of Arrandale silicon towards the middle of the year with better power characteristics.
If what you're after is raw, unadulterated performance, there are still faster options. We compared Arrandale with a Core 2 Duo P8700, and performance went up. If you already have something with a Core i7-720QM (or other i7 part) or a Core 2 Quad, the performance figures aren't nearly so rosy. The catch is that battery life on quad-core CPUs, frankly, stinks.