Tile5 is a progressive HTML5 mapping library that uses the stuff that "all the cool kids" are playing with and makes a mapping library with it.
- Is it the most stable new mapping library on the planet. No. It isn't.
- Is it the most activately maintained mapping library. Definitely not.
- Is it the fastest mapping library around. It's pretty good, but probably not.
If you are up for a bit of experimentation with your mapping, and you are keen to see what is actually possible, then I'd certainly say have a play with Tile5. There are lots of other good libraries out there though, and I'll get a comparison up of them on the Sidelab blog as soon as I can.