I have the Doc BB in Colquelicot and I've been carrying it everywhere. Crazy about it!
Yes, IMO, it definitely can be used as an every day bag.
With regard to the one handle, on the BB, it works fine. It looks good, it carries well in the hand or on the arm, looks fine with the strap. I have no problems with it. In fact, I love the uniqueness of the one handle.
That said, I'm not crazy about it on the PM. To my eye, because the one handle is placed behind the zipper, on the Epi bags it makes looking at a large plain space. On the Losange Docs there is a pattern to catch the eye, so looks better. I also think the PM would look better with the traditional two handles.
Needless to say, that is simply my opinion, fwiw. I'm sure many other tPFer's would not agree. That's why they make so many different bags!!!
.....and I seem to want most of them...my wallet is running away in fear...