Mud 2s are the most popular clinchers here in Seattle by a large margin. I ran them all last season and just picked up another pair. They're inexpensive, supple, robust, and work well in a variety of conditions from greasy grass to boggy mud. My only complaint is the profile on a wider rim. On 23mm rims the side knobs don't sit quite far enough down the shoulder of the tire which means they break loose a little early if you really push them in some situations.

My teammate is running PDX clinchers and loves them. They do run big. Of course the Mud 2 is also bigger than its claimed 30mm.

I think the Limus is kind of overkill for all but the sloppiest conditions. The tread is extremely chunky. Also, they are expensive, and the Challenge tread is glued on, which means it can separate. Finally, gum sidewalls can get nasty. If I stick with this cross thing I think I'd eventually like a set of the tubulars for really nasty days, but not as a general purpose tire.