Got the dual last time they were on. It’s great (clamped to the back of my desk, still holding strong. I’d expected to need to drill through, but the clamps have done just fine so far).
One word of warning, though: you can only adjust the vertical positioning of both arms together. There’s no way to nudge one monitor up or down an inch or two to match the other. So if your monitors aren’t twins, check the placement of the VESA mounts.
I’ve a 19" old-style 4:3 and a 22" 16:10, chosen so the screens and bezels matched up quite closely on their stands… but once I mounted them, since the VESA holes aren’t in the same spots, the left screen is about an inch higher than the right.