Dan, The Axe in general remains unchanged from the first models to now. The early ones do have an optimus board which works fine, but I believe that in the newer ones they have changed to a Shockwave board (only difference is that the newer board saves your settings when you do a battery change whereas the first ones if you took longer than 30 secs to change your battery then you needed to redo your settings) apart from this they are the same gun.
Here is my thread I have of one thats available now;
http://p8ntballer-forums.com/threads/empire-axe-z2-and-barrel-kit.163667/
This gun has worked flawlessly since new. It is my mates gun but I have always teched it for him. It was last used at bricketwood on the 8th december. Its only available as we are changing to the Vanquish next year. I still have a XSV Ltd Edition Axe that comes in custom colours and a redline grip and a standard Axe in custom Anno colours with a Shockwave board - Both of these are standard and are as good as this one thats available. I really do like these guns and dont want to change to the Vanquish but as a team we are changing so have to go with the times. Both of these will be spares in the kit bag and if I have problems with the new gun then know I have got some healthy back up, but if the Vanquish is as good as the Axe has been then I think these may just be gathering dust.
If you play at Bricketwood we will be there for the Masters series and you are more than welcome to come say Hi and have a go with either gun. The other benefit of the Empire Guns is that these are still in production and so spares are not a problem.
I know that Plant have a excellent aftermarket sales service but with some of their older guns you may have a little problem in getting some spares.
Phil