Just to offer another opinion, to make things more confusing....
Peronally, I lump Tamron and Sigma together. They're both top-rate third party lenses. Astro's labels based on tiers is fair enough. I'd call both of those Tier 2. My Promaster, as an example, I'd rate about Tier 7 (or however low it goes). Canon and Nikon (who I also feel are equals) both make some AMAZING glass, if you're willing to pay for it. I've used the 28-300 Tamron on a Canon, and it's very versatile, certainly. Having used third party lenses, I have a personal preference for never stearing away from Canon any more, but that's just me.
As an answer to your question, Tamron isn't junk, but it's not Canon, either. How do you think you might use your camera? That would help decide lenses for sure.