Its funny that you mention a PRL update. I just got back from a Sprint Store, where I had taken my NS4G in for service after GRJ90 did nothing to resolve my signal issues. After the tech worked on it for 20 minutes or so, I came back from lunch and they said they fixed it with a PRL update and reprovisioning data (Update Profile). I found that pretty interesting since PRL and Profile updates have been failing on my phone since the text message outage a couple weeks ago. After I left and got my phone back, I checked the PRL version, and surprise, surprise, it was still the old 60679 version that its been on for the last couple months (latest is 60680). I don't know if they intentionally lied to me, or if the tech is incompetent and doesn't know how to do a PRL update.
When I asked about how this addresses my 4G issues, they did some more diagnostics and after 45 minutes determined that my 4G antenna is bad and they're going to give me a replacement phone. Something tells me I'll be back soon.... (luckily the Photon comes out on Sunday, maybe they'll go for that as a replacement!)