Hi,
I am completely new and a bit puzzled about Pixy2 features. The short video says Pixy2 can do the same stuff like its predecessor or even more…and that seems to be all. Hence my questions:
Hello Adam,
Thanks for the message. OK, to answer your questions:
What would be benefits of choosing Pixy2 over Pixy1?
Pixy2 is smaller and faster and does more, including the line-tracking algorithm. The line tracking algorithm might be back-ported to the original Pixy, but it won’t run as fast. Pixy2’s image sensor is also an improvement. It supports increased framerate with cropping and has an image flow processor for color and gamma correction.
Does Pixy 2 have a narrower field of view? Some third party says it is only 60 deg horizontal, 40 deg vertical
It does and those numbers are correct – we will put on the wiki (https://docs.pixycam.com/wiki/doku.php?id=wiki:v2:start) We expect some people will not like the narrower field of view. 
The advantage of a narrower field of view is the lack of pincushion distortion and a small resolution boost, although the FOV is modestly smaller – 60 degrees vs 75 degrees for Pixy1.
Does Pixy 2 have a replaceable lens? As I know Pixy 1 uses M12 standard.
You are correct, and Pixy2 doesn’t support a replaceable lens. We also expect some people will not like this The advantage of the Pixy2 lens is its much smaller size and factory-focus.
Is there any dedicated website/wiki for Pixy2?
There is! 
https://docs.pixycam.com/wiki/doku.php?id=wiki:v2:start We’re a little behind the ball on it, but working to get it fully comprehensive.
Edward
count me as vexed by the lack of replaceable lens. all other improvements are sweet.