This lens is sharp, light, relatively inexpensive and well constructed. I use to think the down side to this lens was it's constant F/4. But through the forums I've learned that the F/4 lens are lighter, cheaper and sharper than the F/2.8 counterparts.
The 16-35 F/2.8 might seem tempting for low-light needs but the price and (from what I heard) IQ might not be worth the dough at almost 1400 USD. That's double the cost of this lens. Since most of my Wide Angle usage is for outdoor the f/2.8 is unnecessary.
When I first used this lens I thought it was the biggest, heaviest lens ever. But now I know better, its the smallest, lightest L I own. haha.
I don't think you'll be disappointed by this lens and if you decide to sell, it retains its value well.