Same here. I have been using Ubuntu One file services extensively on a free account while at university to backup my assignments, projects and whatnot. I used the service because for me it was better than the Dropbox app and it integrated nicely in Unity (though that could have changed in the mean time, I haven't checked it in a while).

This being said, it did have its warts (for example sometimes when uploading a file the app hung for no reason; there was even one time when I had some files reverted to an older version).

I understand their decision and I think it is better to discontinue a service than to keep it running without improving it. I guess it's time to switch...