I looked at a few e60's before buying my e39 bud. They suffer with quite a lot of issues like MSG pumps and also oil pumps too. The fuel consumption is early teens and the build quality is shite!
They are about the price of a really decent e39 as they are perceived to be the worst m5 built by bmw, and the e39 is believed to be the best.

I wasn't impressed with the build or ride of the e60, but boy do they go well!