Are you removing quilting, or taking apart blocks? I haven't used a trimmer myself, but I saw someone removing quilting with one, and I was *amazed* at how fast it went! If I was removing a lot of quilting, I would buy one in a heartbeat to try it (and return it if it didn't work well). For disassembling blocks, I would stick with my seam ripper - it's fine for single seams.
When I saw the moustache trimmer being used, there were two people working together. They laid the quilt out backing side up (so that if they nicked the fabric, they didn't ruin the top). Then one person pulled the backing up while holding down the batting and front, and the other person did a back-and-forth with the trimmer along the backing. They basically peeled the backing off (it kind of reminded me of skinning a carcass). The moustache trimmer meant that more than one line of stitches could be clipped at once, so it went really quickly. They removed the fairly dense FMQ from a full-sized quilt in about half an hour. Obviously they had practice, but it worked really well. They used a sticky lint roller on the front to get off the thread bits.