[Klaus]

http://www.tamron.jp/en/product/lenses/a037.html

[toni-a]

Seems in the middle of nowhere, Tamron themselves already have the excellent 15-30f2.8 stabilized 100% worth the price difference
also for the same price you can have tokina 16-28f22.8 28-35 area is usually covered by another zoom for most users

[Brightcolours]

Seems in the middle of nowhere, Tamron themselves already have the excellent 15-30f2.8 stabilized 100% worth the price difference
also for the same price you can  have tokina 16-28f22.8 28-35 area is usually covered by another zoom for most users

Doh. Both lenses you mention are heavy and have a large protruding front element. 
This Tamron is more compact, much lighter and can use filters and a normal lens cap.

Clearly it has its own place.

[Rover]

Seems in the middle of nowhere, Tamron themselves already have the excellent 15-30f2.8 stabilized 100% worth the price difference
also for the same price you can  have tokina 16-28f22.8 28-35 area is usually covered by another zoom for most users

Doh. Both lenses you mention are heavy and have a large protruding front element. 
This Tamron is more compact, much lighter and can use filters and a normal lens cap.

Clearly it has its own place.

Yeah, that Tokina is twice the weight, has no filter thread (even though it's 16mm at the wide end, not 14mm where such a construction would've been excusable) and only goes to 28mm on the long end... and all the while the performance is not magnitudes better (per Photozone's tests) than the rivals. Of course it beats the old Tamron 17-35 but it's not a big feat. Let's see how the new one fares... (and yes, it's designed to clearly slot below the 15-30 in the lineup).

[miro]

Positive
- compact
- lightweight
- accept old standart filter size 77mm. Most photograpers already have then.
Most likely positive
- simple construction with modern coating translates to better flare resistance. Something ecential by lanscape shoots.
- missing IS - is mostly guaranties for longer life
Negative
- It is not UWA - my oldy sigma 10-20 is wider on APS-C than this one.
- The MFD is not spectacular low to reaggregate the UWA images.
sum-up
- Canon 17-40 is L lens has beter resell value and similar price/
The situation will be different if Tamron drops RSP price

[Rover]

Not sure about the 17-40's "resell value". At least here the market is awash in these because they're the "starter lenses" everyone buys when they think they have to go FF, and later dumps for something better/faster. They're dirt cheap even at the current exchange rate.