Not to
burst anyone's bubble, but this theory
makes no sense astrophysically. First, an object entering the
solar system from outside will enter with a
velocity similar to the
velocity dispersion in the
solar neighborhood, say about 20
km/s. In order to be captured into a solar orbit the
interloper must lose all that excess energy through two-body interactions with the other planets. It's not easy to
design a scenario where this happens, let alone get it to happen by
chance. Download an
n-body simulator and try it.
What's more, although the rotation of Venus is unusual as compared to the other planets, the orbit of Venus is typical. As e-troon mentioned, Venus' orbit has a very low eccentricity; it is also inclined only 3 degrees from the ecliptic (that is, its orbital plane is nearly lined up with that of the earth and the other planets). The probability of this situation arising from a chance capture is basically nil.
As for the craters of Venus, there is an extensive discussion of them at:
http://www.eoascientific.com/prototype/newcampus/space/11/venus/venus2.html#general
The executive summary is that there doesn't seem to be anything about them that can't be explained by known processes.
The problem with this theory, in a nutshell, is that it focuses on one or two odd features of Venus while ignoring all the features that are perfectly ordinary. You could do that with any of the planets; all of them have something strange about them if you look hard enough. If you consider all of the evidence, there is no reason to believe there is anything exceptional about Venus.