Panhard brace: Pass.
I know that if you pull the factory unit out it really does appear flimsy as hell (it'll easily twist in your hands). But that's subjected to twisting forces it's really not intended to resist in the first place. FWIW, I have one, because it was cheap and I bought into the "flimsy" argument. Then this summer I saw the FR500S cars running times I could only drool over...and I'm pretty sure they were using the stock brace. I guarantee those guys are running harder than you or I ever do (for the foreseeable future...).
The lower control arm brace is something that Ford thought well enough of to include it as standard equipment on later cars. So that deserves some love, I think.
The general consensus I've seen on the front upper strut tower brace is that it's largely window dressing. Some look pretty cool though. I have one...`cause it doesn't cost me points (NASA TT) and it looks cool. =)
Best,
-j