sigma 18-35mm f/1.8 aps-c lens

[DSLR_Newbie]

This Lens sounds great and the DXOMark score is very good.
My question is how useful would this lens be ?
Here is my take on this and I might be completely off here so please feel free to correct me if i am wrong.
Consider the scenarios

A. Landscapes Usually F8 or higher is preferred for large DOF. so F1.8 wont be that useful.
B. For group shots the DOF would be really thin. So a Smaller Aperture would be useful.
C. For portraits it sounds great but there are other primes in that price range. the 18-35 range is not great so even with a prime you can walk forward or backward (most cases) to get the shot.
D. Walk around lens : The range is too small to be carrying this lens only.

I love the idea of owning the lens and I think this might be a great lens for people to start with (ditch the kit lens and get this) but for people who already have a few lenses like 17-55, 70-200mm f/4 L,15-85mm f/3.5-5.6 IS Lens and 10-22 this might not be the ideal lens.

[conropl]

This Lens sounds great and the DXOMark score is very good.
My question is how useful would this lens be ?
Here is my take on this and I might be completely off here so please feel free to correct me if i am wrong.
Consider the scenarios

A. Landscapes Usually F8 or higher is preferred for large DOF. so F1.8 wont be that useful.
B. For group shots the DOF would be really thin. So a Smaller Aperture would be useful.
C. For portraits it sounds great but there are other primes in that price range. the 18-35 range is not great so even with a prime you can walk forward or backward (most cases) to get the shot.
D. Walk around lens : The range is too small to be carrying this lens only.

I love the idea of owning the lens and I think this might be a great lens for people to start with (ditch the kit lens and get this) but for people who already have a few lenses like 17-55, 70-200mm f/4 L,15-85mm f/3.5-5.6 IS Lens and 10-22 this might not be the ideal lens.

I will be keeping an eye on this one. I would like to see Bryan's review first. I have a 10-20mm sigma and it is fairly soft, and the AF absolutley sucks... I always end up manually focusing. However, Sigma seems to be really turning things around with one good release after another. I use my 24-105mm a lot, and it is at 24mm most of the time. The 18mm would be helpful for me (although 14mm would be better).

I disagree with DSLR_Newbie regarding the f/1.8 max apeture... that is what I really want for night time land scapes. The stars and land elements will tend to be at infinity anyway. As long as I focus at the hyperfocal distance (31.5 feet), I will have a DOF from 15.7 feet to infinity... which is good enough for me. I have been wanting a fast, sharp lens for a while now, and the price for this one is right.

My biggest problem is the weather sealing. I tend to be out in bad weather, and evenings produce heavy dew (espsecially along the Lake Michigan). I am not sure how the lens will hold up for my use, but I do seem to get by with my 10-20mm... my biggest problem has been the canon 50mm f/1.8.

Pat