Here is my take on this:
If I get the $500 rebate (for the HDTV purchase) before the end of April, I will keep the STB. For $250 it is well worth it.
I am not concerned about the quality. The purchase includes a 2-year service plan, so I should be able to get a more stable unit if it becomes available.
My initial purchase includes one extra Plus Pack, and since I am not planning on Va Va Voom, this will be saving me money on HBO.
And when the PVR is released (though, I am not very optimistic about seeing it soon), I will buy it too and keep the STB as a network client.
On the other hand, if I don't get that rebate, I am not so sure about keeping the STB. I might consider the lease option.