A friend and I recently returned from a fantastic mountain biking trip in Cappadocia with Argeus Tourism & Travel. The 8-day package was the first holiday of this kind I've taken. Now that I'm able to compare the experience of herds loading and unloading from busses at major destinations to the more solitary/personal experience of an off-road trek, I have to say I'm inclined to travel this way quite a bit more.
Argeus (and our guide Mehmet Ozden) runs a very smart tour. Our first day of biking was a short one (15 km), which gave us a chance to get the feel of biking offroad (neither my friend nor I are accomplished mountain bikers), but more importantly it gave Mehmet a chance to see what we could and couldn't do. The following days of riding were increasingly long and difficult, but our abilities improved, as well.
On this trip we were able to visit all the major venues an "ordinary" tour would include (Goreme Open Air Museum, Love Valley, Deringuru Underground City, ceramics factory, etc), and did quite a few things you're just not going to do from a bus or car. The rides through lush valleys were particularly gorgeous, and the speed of long and/or steep downhill runs was exhilarating.
The ride was reasonably luxurious - a lot of sweating, of course - we had a jeep following us with all the necessary items (repair kit, first aid kit...), as well as ample snacks, drinks, etc., and our luggage when we moved locations. We stayed in comfortable boutique hotels, and ate delicious meals primarily at local restaurants or the hotels. The only thing that could have benefitted us on this trip that wasn't provided is handles installed on the jeep to drag us up some of the steeper climbs ;-)
A note about Mehmet as a guide. Mehmet made the whole experience _very_ easy. Hotels were all pre-arranged with no hassles at all (with the possible exception of those last few hundred meters uphill to be pedalled), lunches, tours (as he's a certified national guide, it was as simple as Mehmet taking his bike helmet off and putting on the required badge). There was no pressure for anything - if we needed a break, we took one; if we wanted to spend extra time somewhere, we took the time; if we wanted to skip a particular attraction, so be it.
Mehmet was also accompanied by his dad, who drove the jeep. We found Mehmet and his dad not only to be a good source of local and national knowledge, good fun to be around and speak with, but also accomplished cooks. One day we took a break from biking, wandering around the town of Guzelyurt and Monastery Valley. We joined Mehmet and his dad at the nearby lake where we were treated to the best meal of our trip - dad's koftes.
When we ended the bike trip back in Urgup, Mehmet suggested we treat weary muscles and several days of unshaven growth to a turkish barber (for a shave) and a turkish bath. A great way to unwind, and generally wrap up a great trip.
I highly recommend Argeus for the Mountain Bike Tour, and wouldn't hesitate to use them again for future trips to Turkey. I'd also highly recommend Mehmet for your guide - knowledgeable and a lot of fun to spend time with, Mehmet was a big part of the reason this trip was as good as it was.