I've chimed in on forum posts before about this before.... Bad move, Esri. Many of us have built Apps that utilize one or more toolbar controls. I get it - It's not part of the "core" functionality, but now we have to reinvent the wheel. Ya, we can download the SDK off of CodePlex, but this comes at the cost of bloating our .XAP. We can "rebuild" a toolbar using a stackpanel and buttons/images/etc. But, there's the keyword - "rebuild". Other depreciated controls like the scalebar were replaced with an alternative (scale line). Not the case with the Toolbar.
Why give-ith if your are going to take-ith away?
Here's an idea, Esri: how about a blog post on how to migrate from the Toolbar control to your own, custom control?
Just my $0.02.