Hi lemonswade, welcome!
I didn't realise you were in Vancouver when we started talking about the FMQ stuff from the Slant yahoo group. I think a 15-91 is a great machine, I used to have one, but it went to a working home, as opposed to sitting in my sewing room looking longingly at me every time I walked in.
The 15-90 is pretty much the same machine, but with a belted motor instead of a gear driven motor. For FMQ, the "power" of a gear driven motor isn't a necessity. My first (and so far only) actual quilt was FMQ'd on a 15-90, the one in my sig. It didn't so much as hiccup. Some people also say some of the clones are even better than the Singers.
I tend to prefer the 301 for FMQ, for 2 reasons:
1. I sew more if I leave the house. The 301 is -way- lighter to carry around, even to another room of the house.
2. If I want to watch TV, or carry on a conversation, or just not have the neighbors lodge a noise complaint, I use the 301. The 15 is a fairly loud machine compared to many others, even other singer made machines.
Feed dogs don't have to be dropped or covered. Just set your stitch length to "0" and go for it. This is what I do even on my 301 which is dead easy to drop the dogs on. I think this is part of why I can FMQ on a 401 too, not raising the plate removes one more issue to overcome.
The other thing to do is turn the machine so the nose faces you. This overcomes the issue with throat / harp space, which is the biggest complaint about the 301, but the 15 isn't so much bigger that you'll think "Hey this is downright roomy". It's nothing like the newer machines built for quilting, but it's also not priced in the multiple thousands either.
