Assembly was straightforward once all the parts had been inspected. It took me about half an hour to set everything up. The first stand took longer because there aren't any assembly instructions, and I initially spent a good 10 minutes making sure I knew what went where before proceeding. Once I knew how it all worked, putting together the second stand probably took just over 5 minutes. Make sure you pay attention to which direction the stand tilts when screwing it all together though!
There's a screwdriver included, which is handy; although I now have 2, which is unnecessary. It does seem a bit strange than you can't buy a set of 2 stands, as I can't imagine there are many people with just a single monitor.
The ability to tilt the stand is nice, and given the generous height range available, you shouldn't need to tilt them much anyway. They seem solid as a rock with the monitors on them.
These stands are not the best looking pieces of furniture in the world, but I've got them behind my desk, so no one will ever know. They aren't hideous, but most definitely fall in the category of "functional".
Kudos to Gravity for clearly listing the materials used on their website, which is a blessing if you have a serious allergy to certain substances (in my case, natural rubber). If only more manufacturers would do this!
