Nikkor 18-135mm f/3.5-5.6

General
This lens used to be hot stuff a few years back. It was longer than the 18-70 (the basic kit lens for quite a few years), way longer than the 18-55 (another kit lens), and quite much sharper than either of them. In terms of absolute sharpness, this was and still is an incredible lens. But is it enough to be a great lens? Read on, and you'll see why sharpness is not the only - heck, maybe not even the primary - thing to worry or be excited about in a lens.

Pros/Cons
+ incredibly sharp throughout the range
+ great range, 18-135 covers from wide angle to tele.
+ pretty compact and light for being a superzoom

- no VR
- sharpness might be great, but there are several important flaws: vignetting, distortion, and chromatic aberration
- let's not forget it's f/5.6 at 135mm. Autofocus can be problematic in low light

Intended Users
Great for:

• if sharpness is the absolute top priority and you can live with the drawbacks and you need a superzoom, this is your lens
• as it all comes down to value, if you happen to come across a cheap (or even "free"/bundled with a camera) copy, ultimately it's a great lens.
• all in all, a good lens for a very small window of needs (read "Final Verdict" below)

Check out the sharpness of this lens! Impressive, I must say

Not for:

• if you can afford the 18-200VR, it's clearly a more balanced option
• if you don't mind the slightly shorter 18-105VR, that's also a clearly more balanced option
• lack of VR might be a show-stopper for some people.

Final Verdict
I struggled a lot to find something to write on the "Great for" section above. And I felt it's unfair to the lens, because it's ultimately not a bad lens. It's a typical example of marketing strategy errors rather than designing ones. The problem with this lens is that it costs to make (it's not overpriced; simply it's priced for what it is: a superzoom with stellar sharpness throughout the range) and as a result its value is on very questionable levels, particularly in a world with the 18-105mm, the 16-85mm, and the 18-200mm - not to mention third-party options. All of the above lenses have VR, which the 18-135mm does not. The 18-105 is cheaper and almost equally good (in terms of sharpness; in terms of overall performance it might even be a bit better); the 16-85mm is more expensive but quite much better; and the 18-200mm is more expensive, it has more range, and of course it has VR.

If the 18-135mm had VR, I would very warmly recommend it. Vignetting, distortion, and chromatic aberrations aside (all can be fixed more or less during post-processing), the optical quality of this lens is superb. For some very particular needs (e.g. if you shoot landscapes and need the sharpness, if you travel light and can carry only one lens, and if you need a range greater than 105mm) then this is a good choice - though take a look at the Nikon Nikkor 18-140 as well.