If there is one bow that I would ever call myself proficent with, it would be WWS as it was my main choice of bow for my Mangudai or "BowaBarb."
I full agree with Omikron in that most people look at the low damage of WWS, even in it's upgraded form, and give it up in exchange for Faith, WF, or God forbid, BotD. As I have tried to show, raw damage alone does not a good weapon make. The Mangudai banked on using Deadly Strike, Open Wounds, and Crushing Blow. Things, which to be honest, I rarely see on Battle.Net as most people shout "ZOMG!!11 DEW U HAV WF?!/1 I R TRAYED 32020 KTHNX???//"
However, I'm rambling. There are still things that I like about WWS than most high end bows. For one, cost. I picked up a WWS for a single Dol Rune. Looking at what Faith requires for runes, WWS is by far a better choice for building on a budget. Next, between the Magic Damage and Amp, I very rarely had an issue with PIs, even though there were those damned PI/MI bosses that occasionally appeared. Flexability on WWS is also nice in the 2 sockets. A pair of Shaels did me good as I tore through Hell.
In the end, if you have a Faith, WF, by all means use them. If not, just grab a WWS. You'd be surprised at what that little bow can do.