Check out Frutiger Next, which introduced oldstyle figs in the opentype fonts.

I've seen them in specimens, but never in use.
In the documentary on Frutiger Next, Adrian Frutiger does a quick sketch of the oldstyle figures (in which he makes a mistake on "4"), which Akira Kobayashi implements (fixing the mistake).
So I don't think the designer's heart was in it (really, it's a feature made to accommodate Adobe layout apps and the OpenType format), and a bit of a travesty for this modern typeface.

What's the mistake?

I disagree.

Unless you are setting tables or columns of numbers, 'old style' figures look more 'natural' within blocks of text on a page.

But, that's my opinion :)

What's the mistake?

IIRC, one of the characters which normally has a descender was standing on the baseline; the 4, I think.

3, 4 and 7?

This site gives the best online showing:

http://www.identifont.com/find?font=frutiger+next&q=Go

Correct though they may be, don't you find the oldstyle figures quaint in proportion and busy in comparison to the sublimely modern reduction of the alphabetic characters?

A version of Frutiger Linotype with oldstyle figures was at one time (and may still be) included with Microsoft Reader, a free, downloadable application for reading eBooks on Windows-based devices.