My initial comments:
Tamron 28-75mm F2.8
This is an amazing lens and i am already in love with this one.
The target was to get a general purpose walk around with a little larger focal length than kit lens. Also, portraits were in priority.
My mind was stuck for Canon 24-105mm f4 L but $1,000 price tag was freezing any move. Then i discovered about this Tammy. Almost all the reviews declared this one to be equivalent in image quality from 28-50mm to Canon 24-70mm at F2.8 and Canon 24-105mm at F4.
Its only weak point is longer range i.e. 60-70mm at F2.8. But when u stop down to F4 to F5.6 it is again very sharp.
I also compared it with nifty fifty and between 28-50mm there is hardly any difference in clarity or sharpness from f2.8 to f4.
Reviews say it hunts in low light and slow on focusing but to my needs its just perfect in focusing as i am no wedding photographer 
This lens has some 'variation in quality' issues so you have to keep your fingers crossed for a good copy.
And ... i was lucky to get a good one 
Now the price .... Its normal price tag is between $400-425 with rebate.
I got a used one from Ebay for $325 which is a BIG bargain for me 
as the copy is in just perfect condition.
And the biggest benefits of all, f2.8 .... I can shoot anywhere indoor now with zoom available and it stays 2.8 throughout the focal length.
Also, very nice bokeh and background blur.
This lens is NOT for distant objects shooting. I tried to shoot far away objects with this at 55-70mm and compared it with my Canon 55-250mm with same range of 55-70mm. F stops were between f5.6-f8. Canon beats it at all f stops in clarity and sharpness.
So, the best uses would be indoor, portraits, street, bokeh shots, macro as well since the minimum focus distance of this lens is only 13" for whole focal length.
