Whole lotta people upset about this, and no surprise. While I’ve been using OSM and OCM a lot already (they’re what’s on my garmin), the loss of satellite and aerial is really difficult to work around for me. Am really quite angry this has been done, and in such a way that has broke many aspects. The mapping options they give are really weak for the UK with two or three just giving white screens.
Fortunately, if you use firefox or chrome, the excellent greasemonkey script is being worked on and the author hopes to have google, OS maps (1:25k), and aerial maps back in play soon.
The script is over here. Broken at the moment since the change, but worth keeping an eye on; http://userscripts.org/scripts/show/109145