I am also being tempted to get rid of my PIII-700@933 & Abit SE6 and get T-bird & KT133. So far, it seems that copper T-birds have a good chance of getting 1.1G - 1.2G or even more while alum. T-birds get 950Mhz - 1050Mhz.
The key is up to what T-birds get copper for sure as I do not want to order one and it turns out to be alum, and it seems like most, if not all, 1G+ T-birds get copper. An the chances go down as the speed decreases.
I perfer buying retail chips over OEM, but it seems that 950mhz is the highest you can get in retail package. Buy.com, Onvia, and others list retail 1Ghz but they are all out of stock.
If I did go for it, I would not get 1.1Ghz or 1.2Ghz but probably get 1Ghz unless chances of getting copper are as good with 900Mhz or 950Mhz.
If any one knew more about what % of what speeds get copper, I would be very much interested in knowing.