For many years I used Darcs as my only DVCS...some time ago I explored Monotone which I like as well.
However, the main problem with both is the lack of complete hosting
Interestingly enough, but recently (after I've asked this question), Fossil got import & export commands, so that now it's possible to use Git's fast-import/export protocol. (See Import And Export".) :-)
No need to tell, but it makes Fossil perfect tool for my DVCS needs and the above dilemma is resolved to my upmost satisfaction. ;)