In reply to TobyA: Ha! Yes I bought one at the same time as you as they were such a good deal on CRC. Since then I've upgraded via a Ribble and two Scott Addict frames. I keep the Mistral in the garage for other people to ride when they visit without a bike and occasionally ride it as it is a perfectly good bike but I do feel pretty beaten up afterwards if I ride more than 50 miles on it!
I regularly do long rides but have never been over a hundred miles on it, it's just too rough. My other bikes are so much more comfy. The Addicts in particular are really very good. When you do upgrade I'd thoroughly recommend buying a second hand, premium carbon frame that's a few years old and swapping the groupset over. That way you can get a very, very good bike that was silly money a few years ago for quite a good price. Something like a Cannondale Super Six, Colnago C59, Canyon CF SLX, Scott Addict. And it will be an exceptionally good ride.
But you should probably not read or listen to any of this. I was perfectly happy with what I had until I rode someone elses Addict and thought 'blimey, this bike is amazing!' Ignorance is bliss