The build quality is good. Tamron's XR Di series is well made. The lens feels solid and has enough weight to help stabilize focusing. However, the lens is not a heavyweight pro beast by any means and is very easy to use all day long. The mount appears to be either hardened aluminum or chromed brass, finishing is good, and lock-up is tight. The VC control is single-mode, however Tamron's normal mode for this lens is 3-way: up/down, left/right, and diagonal. So Tamron has incorporated a state-of-the-camera-art motion sensor/compensator. There's a lock switch to keep the lens from creeping during normal carry on a strap, which is useful because the weight of all the internal lens elements can pull down the barrel while you're walking.
The lens uses 67mm filters. I always use a clear protective filter. The plastic lens hood is a petal shape and fairly short to accommodate the 28mm end of the range.
Cons: The lens hood does not lock securely in place because the retaining detente & tab moldings aren't prominent enough. Some people are addicted to hoods. I'm not. The lens coatings are good enough to obviate the need for the hood most of the time anyway, so I say leave it in your camera bag unless you're shooting in sunlight at shallow angles, or near water or expanses of glass (in which cases a circular polarizer might actually be a better choice). Some lens flare and ghosting in conditions that just don't bother other lenses, and complete absence of flare and ghosting in situations that hammer other lenses. Like other long zooms, the lens will creep on its own while you're walking around, so use the zoom lock switch to avoid accidentally bashing an unexpectedly extended barrel. Although performance is very good, the zoom and manual focus rings feel cheaper than the rest of the lens. Vibration Control (VC) works extremely well in three axes (left-right, up-down, diagonal), an advance over current two-axis Nikon VR and Canon IS designs, but you'll need to get used to the noticeable whirring sound whenever VC engages, as well as the significant composition shift in the viewfinder when VC disengages.
Pros: All in all, the Tamron AF 28-300mm XR Di VC LD Macro zoom is a very good lens with a feature set that is currently unrivaled. I think anyone who takes some time to familiarize themselves with this lens will end up getting consistently fine shots with it for many, many years. Basically, if you never tell anyone looking at your best shots that they were made with this Tamron, nobody will ever think you're shooting with anything but a perfectly good lens. Tell experienced photographers ahead of time that you used a 28-300mm zoom to make the photo and they'll automatically begin looking for faults because, as every photographer 'knows' there are just too many technical optical trade-offs required to design a good 28-300mm zoom. Color them wrong now, because this lens is almost as good as the superb Nikkor 18-200mm VR zoom and I don't make that comparison lightly. The Tamron AF 28-300mm XR Di VC LD Macro zoom is an ideal walkabout lens for non-critical photography of all kinds with almost any Nikon or Canon digital SLR body (full frame sensor or APS-C sensor), and is also a lens capable of making a wide variety of critically accurate photos as long as you've got good light. The central through middle diameters of the lens are very sharp at all apertures. It's a very good, general do-it-all lens for daytime walkabouts, a fine travel lens, and it's also built well enough to withstand regular use for many, many years. Tamron's VC works extremely well. Highly recommended.