Thank you very much marmad, I had seen this Application Note, and the truth is that Rigol has done a good job.
I am impressed with the DS2072.
I compared it (at 20MHz BW) with an old analog HP1222A, from the viewpoint of noise and refreshment, and the refreshment in both screens is very similar (as far as my eye can discriminate). And in both the noise level is very low for a BW of 20MHz. Awesome!
With the DS4000 series also occurs this fall for t<20ns? You have a table?