hey sarah, i've got them on my table. i love that it gives an extra 6 inches or so width to my table. i don't actually use the velcro though. i tried it at first but the sticky of the velcro kept coming off of the table etc. so they lay across the table and then there is a strap that connects under the table too. again, i like it. i have about 4 or 5 layers of stuff on top so you can't feel the straps at all.
keep in mind that the arms are not incredibly sturdy on the table, their there more for extra space for the arms. the do move just a bit if you put too much weight on them. meaning, if you push down really hard on just the arm part, it will shift down a bit. i've never had a problem with them. i really love having them on my table.
let me know if you have any other questions about them!