I've heard several complaints about GT over the years. They are pricey but so far my two purchases have been fair for the money.
I did try the "new" Mullards and was dissapointed... first quad, one was bad, second quad bad tone. I brought them back for refund.
So far as for over the counter tubes Sovtek, EH, Tung Sol, Svetlana, JJ, Ruby and Mesa have all been good to me.
I also did a bulk purchase of some tubes from the 50's and 60's this was my best purchase to date. Of the 200+ Tubes I bought I threw out one bad one... I bought them as is where is/tested from a local soarce... I have a batch of about 100 12AX7's coming soon.
Khing