I've been running into this issue since we started testing on an actual iPhone, not a simulator: the build process seems to hang, for up to 5-10 minutes, without any feedback of the process. After some time, it starts, but it is incredibly annoying that I do not know the status of the build, and what's taking so long. Happens both on the OS X Xamarin Studio, and from VS2013 too. On OSX, I get some small updates, but hangs a lot on some steps.
WP and Android builds have no such issue.