21st, i changed my post to say that no one has pushed a "pure helicopter" to 250kts. And indeed congrats are in order for the BA609.
The V22 is generally cited for tiltrotors, but the discussions are not favourable because of the high disk loading in hover. This means the tiltrotor does not lift as much payload as a comparable helicopter.
The reason X2 has generated such interest is that it has the diskloading of a conventional helicopter, but also overcomes the retreating blade stall limitations. On paper this means X2 derived machines will gave tiltrotors like the BA609 a run for their money.
X2 will open the door for a new generation of helicopters...
