While I am a bit unnerved that it seems to take significantly longer to receive a reply, the delays could have been due to the changeover, a large volume of notices or just the fact it is summer and many people are likely on vacation. The important thing is that the information is valid and Myspace is still cooperating.
DeviantArt Changes Contact Information
In a similar story, DeviantArt, the popular art community site, has likewise changed their DMCA contact information. If you need to send a notice to them you can get the updated information off of their site.
From all appearances, the information listed on their filing with the Copyright Office (PDF) is no longer valid.
This seems to be part of a trend where Web hosts are no longer relying on the USCO to host their DMCA contact information and, instead, are using their own sites to make the information public.
More on this trend later.