Sigma Lens 18-200mm F3.5-6.3
Minimum Aperture: F22
Lens size: 62mm
Optical Stabilization

Most important question to me when I read reviews is: Is it worth the money? Sure, you can compare this to every lens out there the same way consumer reports compares a mercedes to a hyundai; but you have to take money into consideration. This lens is definitely worth it's price tag.

Now to get to all those other comparisons. I bought this because canon didn't have anything with this large of a zoom range on it and I wanted something very versatile when I only go out with one camera and one lens. And even after purchasing several other lenses, this is still the one I go out with in that situation.

It also has an extremely good focus on short distances, so I get some use out of it "macro" wise. There is a shot in my portfolio of a dragon-fly and I think I was about four inches from it with the lens zoom all the way out to the 200 mark to get that shot.

The one shortcoming it has in my opinion is that it doesn't find focus very well at all in low lighting. I have had it go back and forth right past the point of focus trying to lock onto something, even if it wasn't something moving. And unfortunately I shoot a lot of things in low light that are moving, so it always gave me trouble there. (I have a canon lens I use for that type of shot now). It also has not wanted to focus at all a couple times, but I just flicked the AF/MF switch a couple times and it started working. Could have been a dirty connection I suppose.

The other thing about it, which you can see by the F-stop range up there is that is is not a very fast lens when zoomed out. This has been only slightly problematic for me a few times. Mainly if I set my camera up manually and zoom back and forth a lot, I'll end up with underexposed pictures when I'm really zoomed in (or the reverse depending on how I set it up). So I'll shoot less on manual when I shoot like that.

The optical stabilization seems to work well. I've never specifically tested it. But it does seem to make a difference when zoomed in. The lens itself is a bit noisy when working, especially the stabilzer.

Last thing to mention about it, which I really like is the lock for the zoom. There is a little switch on the lens that lets you lock it so when you are pulling it out of your bag or just letting it hang, the lens won't start to open up and lengthen. The lens itself is pretty tight and you might not have much problem with that anyways, I just wish this was on all my lenses.

Main thing is though, is that it is totally worth the money. Anyone with a canon SLR that wants to pick up a decent lense, please avoid the overly cheap basic (and no stabilzation) canon zooms you see and just pick up one of these. If canon had one like this, even more expensive, I would pick it up because of how useful it is. But for what it is, it's a great buy and one of the best single lenses I have.

Update: Canon has now come out with their own version of an 18-200 lens and if I was buying initially...I'd probably go with the canon version. Their glass quality and overall make usually seems to be better. I also prefer their image stabilization. But the difference isn't enough to justify me buying it after I own this lens. Now if it were a "L" lens...