I've owned one for 3 years now. Great, great reel, no question. The 4x8 DC system it uses is the best Shimano offers. I also have a Calcutta DC with the 1x8 DC system and, while it works well, can't touch the 4x8 for adjustability. I have it on an NRX853 JWR and it's a great pair. I use it for a little of everything, given the flexibility of the reel. It will cast most any black bass lure like no other. I also own Steez's, Core's, Premier's, MGX, etc. All nice reels in their own ways, but the Calais DC is just the king for all around.
They are not flawless, though. They are HEAVY. That is the biggest reason I don't own more. If Shimano came out with a version in the 7 ounce range, I'd be all over it. But I recently got info from the shimano rep that is on a lot of the forums that the Calais is not changing anytime soon, and the 4x8 system is not going to be put in any other reel. So I am looking to pick up another sometime soon. Other issues are it is a big reel compared to most of the others I listed above. I have large hands, so it's not an issue for me, but may be for some. It also has a little gear noise, especially under a load like a big spinnerbait being reeled moderately fast. Last issue is the metal/chrome finish. I fish all year long here in NW Ark, and that sucker is COLD to handle in the winter.
It's been a completely reliable and solid reel. I maintain my own reels, and all I've ever done to it is clean/oil bearings and clean/grease the gears. Of course, that's true of pretty much all my reels.