Testing mice is difficult, as there is no clear cut way of showing whether it's any good or not. Instead, I will offer you my opinion having used the mouse for a considerable number of hours. This testing involved using it for general PC work such as photo editing, as well as some intense gaming sessions.
For a mouse so obviously designed for gamers this was the first port of call for testing. It just so happens that I'd just bought myself a copy of Bad Company 2, which gave me the perfect excuse to have an extended frag fest.
At first I was dearly missing my trusty old Logitech MX518 - the Pyra just seemed too small and I was constantly missing shots or clicking the wrong button which was rather frustrating. However, I persisted and eventually it started to pay off as I adjusted to the smaller form factor. Kills were coming back to me and once again I felt like I could place my crosshair pretty much exactly where I wanted it. The experience isn't quite on par with a standard sized mouse, but it's 90% of the way there, which is a great achievement considering the size of the mouse.
It also took some time to get used to the Easyshift button, but in the end I found myself using it more and more. If I were to be picky though it would've been nice to have a standard mouse button 4 alongside the Easyshift button. Although you can assign a button to perform the same function with Easyshift, for a button that I use so regularly it just wasn't as fluent. On Bad Company 2, it was particularly frustrating as I use button 4 for melee, and being caught un-aware I simply wasn't able to respond in time. The other option is to disable the Easyshift button altogether, but doing that drastically reduces the functionality of the mouse.
As an everyday mouse the Pyra is reasonable, but again the form factor lets it down. It just lacks the support that a full sized mouse can offer, reducing the overall comfort of using the mouse. It's also quite difficult to do precise editing with the mouse, making Photoshopping a bit a awkward. The scroll wheel has a nice solid feel to it however, with a nice solid click as it rotates.
For web browsing and general day to day tasks the mouse is perfectly usable, with the wireless working well, giving me total desk freedom. With the Easyshift feature it also meant I was able to control my music from anywhere in the house - nice.