I've got about 2200 shots on my 5D MkII, using the EF 24-105 f4L IS and the EF 70-200 f4L IS. The camera is clearly up to and beyond the L lenses. The 70-200 may be the best lens I've ever used with incredible sharpness throughout its zoom range and all with brilliant contrast. The 24-105 seems slightly soft in the 24-30 range at wide aperture and even stopped down a little.
I expected high resolution and wasn't disappointed. The big, pleasant surprise for me was the low noise at ISO 3200. This effectiveness makes the f4 lenses very practical over a wide range of circumstances.
I just ordered a 25mm extension tube to use with the 70-200. I think that'll be a stunning macro lens with IS no less. We'll see...
I've fed the images to my 46", 1080p Sony Bravia and the results are stunning, even with deeply cropped images. The big sensor with lots of nice big pixels works great for me.