Have just covered 20+miles on my Bizango, and having 26 inch wheel MTB's I can tell you you will be amazed with the capability of one of these bike.
First, the bigger wheels smooth bumps out nicely and there is so much more grip. My mate who I was following was spinning up on gravel slopes, but I was not. Even mud I was getting better grip, only having problems in deep mud.
Second, the speed. I was amazed at how easy it was to get speed out of the bike and maintain it with very little effort. I was able to cruse at a full 5mph faster.
There are down sides, one being the 'longer' wheel will track ruts easier and make it harder for you to get out, and the other is it dose feel a bit barge like in handling on tight twisty stuff, but if you ask me that is all made insignificant when compared to all the other advantages. Well done Halfords & Voodoo, a top bike for the money with a very good spec list. I love it and cant wait to get back out on it.