steemitstage is pretty much a clone but with the new updates baked in. Once it's finished testing, it'll move to steemit.com. I already logged on and tested it, and it works fine.
The changes enable steemit to run faster and also do some processes in parallel.
Oh thats awesome. Yeah I figured it was a clone since it seemed like it was exactly the same, but a different domain. It would be pretty cool to eventually develop a service for steemit.