There's also a very cheap version of this lens, and you DON'T want it. So please spell out which, exactly, you're looking at.
If it's not the ED version, it's not great. I had the ED version, and while it was a nice lens it lost some usefulness at the long end because it didn't have VR.
First, if it is really the 4.5-5.6, then it's one of the ED lenses - the cheaper G version was 4-5.6.
Second, Bjørn Rorslett tried out that cheaper G version and said it wasn't too bad, all in all. So that runs counter to what I'd heard (and posted earlier), but frankly Bjørn knows a lot more than I do.
As far as the "just because it isn't a 2.8" question: Many mid-range consumer zooms can still give you excellent results as long as you understand their strengths and weaknesses. Usually this simply means you get best results if you stop them down a bit - shoot at f/8 or so and you're golden. Shoot at f/4.5, though, and your results will probably be sub-par. The pro zooms are generally not going to be dramatically better than the mid-range consumer zooms at these middle apertures (I won't say this is always true; just speaking generally). Where the pro zooms really pay off, though, is giving you the ability to shoot wide open and still get great images. Additionally, having a max aperture of f/2.8 means you have a significantly brighter viewfinder image - that can really help you nail the focus quickly (either by providing faster AF or else letting you manually focus much more quickly).
Nikon lenses are neither good or bad. they are either well matched to your usage or poorly matched.
So, how would you use this lens. If you are taking it to Africa to shoot chimpanzees in the wild, I'd say this is worse then useless. but if your subject is relatively static and you can use a tripod and you are shooting in bright sunlight, then this is an ideal lens. Got something in between? then it's kind of a grey area.
It also depends on what you do with the images. Are these going on the web or printed 4x6 inches then you don't need to care about CA or sharpness but it these are to be presented to a professional client or if yu want to make fine art quality prints. These considerations make a big difference if the lens is suitable or not.
There are no "bad" lenses. I have some images in my library I like a lot that were shot with a $20 Holga. For it's purpose that little plastic lens is very good.
Want a "car anology?" Well here is one anyways: Is a Toyota Corrola a good car? We can argue andeveryone will say what they think. Then the next day I tell you I have a wife six kids. Now the arguments are all moot, the corrola does not work for my usage.
Its slow to focus, dark and somewhat flimsy but it works if you've got lots of light. Bokeh is kind of strange. I use a 70-200mm f/2.8 IS for telephoto so I used this just for banging around.
That is some funky bokeh there Taylor.
For speed alone does not make a good or bad lens, depending on the application for which it's used. Now as far as build quality and
resolution of the glass used to build the lens, that is where cutting corners and buying cheap will bite you in the ... you know.
Why buy a cheap lens only to want a better, sharper, faster one in six months or a year? I think you should save that $200 and put it
toward a piece of glass that will give you better image quality, unless you are not too serious about staying in slr photography...
'spend your money on quality lenses that will outlast a couple decades worth of camera bodies'