Right after R2 for Configuration Manager 2012 was released, customers started noticing some excruciatingly slow download times for images. Some have reported that the download from the Distribution Point will peg the CPU to 100%. The reports have been widely distributed, showing that a bug is evident and is affecting any customer attempting to use WinPE.
Microsoft has now acknowledged the problem and CSS has identified the issue. Work has started on a fix, but the fix may be weeks away from releasing to the public. Per Microsoft on the root cause:
"…block size for how often the Task Sequence Progress bar updated was changed and it was updating much more frequently, causing the download the slow down significantly."
Let's hope the fix comes quicker than later, as it is slowing adoption of R2 for ConfigMgr for many.
UPDATE: One individual just posted another workaround today that seems to work. Beany_for_ever chose the "Access content directly from a distribution point" option. This allowed an 8GB WIM to deploy in about 5 minutes.
That's something to try while waiting for the fix from Microsoft. Keep in mind, however, that choosing this option disables the ability to utilize multicasting.