but let me get this straight.
You're running Firefox 3.7 nightly build, and are wondering why the themes do not look like Firefox 4?
Is there a clue there in the different version numbers?
Other than that, since you are beta testing I'm sure the Mozilla team will need to know your findings, so they can troubleshoot them.
I am running Firefox 3.7a6pre (Nightly 6/23/10) but my theme doesn't look like the other Firefox 4 nightly builds people are showing screenshots of. Why is that?