Have you tried the old 18-200mm Tamron lens on your new camera (if you still have the lens)?
I suspect you mean Error 99 (not Error 990). If that's what you were getting with your older Rebel, it's not necessarily a lens problem. Error 99 is sort of a "catch all" code that means little more than "something isn't working right so the camera and lens are unable to function". It doesn't really tell you what's wrong. Might have been the lens. Or it might have been something else.
There is a possible problem using any third party lens such as the Tamron, that it won't be compatible with future camera models. Third party lens manufacturers reverse engineer their lenses to work on current and previous camera models. As a result, if something changes in future camera models, the lens may no longer be compatible.
There's far less chance of this occuring if you use OEM lenses.... i.e. Canon lenses on Canon cameras. In fact, I don't know of any significant incompatibility issues among all the EF lenses made for all the EOS cameras for the past 25 or so years. Canon designs their cameras with both forward and backward compatibility in mind. In fact, it's one of the defining characteristics of Canon's premium "L" series lenses, that they are fully compatible with all EOS cameras past, present and future. The same has been true, though, of Canon's non-L EF lenses. The only exception is EF-S lenses, which are designed especially for use only on APS-C crop sensor cameras such as your 350D and T3/1100D. All EF lenses also work fine on those cameras. But, by design, EF-S lenses cannot be used on full frame (6D, 5D-series, 1Ds-series) or fitted to some of the older APS-C crop sensor cameras (10D, D60, D30) that existed before any EF-S lenses were offered.
While not guaranteed to be compatible with all future models the same as an "L", it's a pretty safe bet that Canon's non-L-series lenses will work fine on them too. So far Canon has been batting pretty close to 100%. .
There are some quite good third party lenses from Sigma, Tokina and Tamron (I use Tamron's 90mm f2.5 and 60mm f2.0 Macro lenses, for example). Some offer features not found on Canon lenses. And third partly lens prices can be attractive. Just be aware of this possible pitfall: If you choose to upgrade to another Canon camera model sometime in the future, the third party lens may not work properly. There's no guarantee it will.
If you buy a new Tamron lens now... a currently made model designed for Canon... It almost certainly is going to be compatible with a Canon camera model such as T3/1100D that's been available for a few years. Where I've noticed the most third party lens compatibility issues is with the newest Canon models that have different and more sophisticated autofocus systems (70D, 7D Mark II, for example). Canon has changed the design of their cameras to offer new features, and in some cases the third party lens manufacturers are still catching up.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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