Sigma 18-50mm f/2.8-4.5 SLD DC OS

[sunburst]

whats your opinion of this lens: Sigma 18-50mm f/2.8-4.5 SLD Aspherical DC Optical Stabilized (OS) Lens?


vs: the TAMRON 17-50mm 2.8 zoom

or vs:

the more expensive Sigma 18-50mm f/2.8? { 100 bucks more }

[ Sigma 18-50mm f/2.8 EX DC SLD ELD Aspherical Macro Lens for Canon Digital SLR Cameras ]


I'm confused, 'cause this is newer , cheaper, and has OS + HSM motor.
{but restricted 2.8 } I can't find too many reviews on it.

And/ or what's your opinion of the Tamron vs the second Sigma listed?


http://www.amazon.com/gp/product/B002330FOI

Opinions?

thanks