I have a pro plus subscription, and I tested that the files attachment feature is really unuseful. I wont to think that all pro plus members, like me, are agree with this experience.
It would be really usefull if it consisted of a Skydrive office online integration, or in a dropbox or google documents integrations.
Next year I'll sure not renew the pro plus subscription, but only a pro subscriprion.
But I really waiting for the feature integration that I explained here. It's the future, It's, for me, the only way.
No problem at all, I don't care what gets implemented, just something better implemented (though skydrive is a tad too MS for me). Right now we pay for XGBs of space for files, at it is just useless enough not to be useful.