Hi

I'm in the market for a 70-200 and I'm considering the 'Sigma 70-200mm f2.8 APO EX DG Macro HSM II Lens' or the new 'Tamron 70-200 mm F2.8 Di LD (IF) MACRO'. Has anyone had any experience with both of these? The Tamron has been out for a couple of months now but there doesn't seem to be any reviews online or in magazines.
Also, will both work with either a Sony or Sigma 1.4x/2.0x Teleconverter?

Thanks