As some of you may already know, I have a Gordon Smith SG-1 with a tune-o-matic bridge. This particular guitar was a wedding present from my wife so it has huge sentimental value to me. It's on the left in the pic below:

Much as I loved it, the top E string never really rang out properly. I changed string gauges and did a setup myself but it was never quite right. It always sounded dull and it didn't sustain properly. I then sent it off to a pro for a setup and it came back better than ever, but still duller on the top E than any other string. It annoyed me.
In a flash of brilliance on Monday, I decided to invest in a lightweight tailpiece to see if that helped. I've already fitted one to my Gibson Les Paul to brighten the tone a touch, so I wondered if it would help the Gordon Smith's problem. I ordered the chrome finish Gotoh aluminium tailpiece (£26.95) from WD Music yesterday around 1pm and it was on the doormat when I got home from work today - that's top service!
I did a quick test of the guitar as stock so the problem was fresh in my mind, then I swapped the tailpieces over and re-fitted the same 11 gauge strings. The new tail is significantly lighter than the old one, so things were looking good. A quick tune up and an open G chord - kerrrrrannnng! Result! The top E rang out like a bell, as did all the other strings! I can't believe something so simple cured the problem. I was almost resigned to the fact that it was a dull piece of wood used in either the neck or the body that was absorbing the higher frequencies.
So to all you doubters, different tailpieces DO make a difference to the sound of your guitar!
P.S. This guitar, with it's Mississippi Queen, sounds awesome through the Little Rock - beefy as a 14oz T-bone :D