Now that I know GBT is on 9000, I'll point my miners there. I don't recall seeing that on the website, and I certainly didn't wade through the 100 pages of data here.
EDIT: it seems stats don't report work if you use the GBT port.

Yeah, it's only for testing. GBT will soon be on the regular port. Port 9000 may be unstable, and hashrate on that port won't show on the website. But you do get paid, and the hashrate will show in shifts, it just won't show as current hashrate.
It's a bit of a hack. In the future I will add proper support for multiple servers and they will show properly in the stats.
BFGMiner interprets the Stratum header as "prefer Stratum over the current protocol", so IMO it would be better if it were only offered to getwork requests.
Good to know, I'll just add the header on getwork responses then.