Today, Sony revealed that the Vita has currently sold 1.2 million units and that game sales have gone past two million. Whats interesting to note is that the game sales includes downloaded games as well, not just sales from physical shops. Another point, Sony have gone on record to say that these are genuine sales numbers and not just "sold to retailers" numbers.
While these numbers might look good, it's worth noting that it is no indication of how well the system will do. The 3DS had a similar launch, hitting just higher than 1.2 million in the same period but was unable to keep that momentum and ended up with a complete slashing of the price a few months later.
This does look good for Sony though, hopefully they can manage to keep this momentum where Nintendo failed with the 3DS. The big problem for the 3DS was that there was no "killer app" at launch and very few saw the point in buying one after the initial rush. Sony does have more of a chance thanks to not only the abundance of launch games but quality of those games and the number of titles still announced for the future. I think Sony has a much better future ahead than Nintendo did with the 3DS at this same point in time, but we won't know how things turn out for some years now.