Yeah, so far, not a fan. But my client is tired of hiring other random firms to help him with it and I've been working for him for about 5 years now and he's ready to just throw some money at me to figure it out and centralize everything.
The worst thing about those Yahoo stores is that most custom functionality cannot be built into the store itself. So as it stands right now, he's hired 2 different companies to write custom stuff and each one has Javascript calls to PHP files located on their servers to make everything work. Unfortunately all I'm really going to be doing is taking all of that functionality and moving it to his VPS but at least it's all in one place and no fear of failure if one of the other companies goes down.