I'm a complete 505 fan, but the fusible batting is good for smaller projects where you would get a lot of overspray from 505. Fusible is particularly good for quilt as you go projects because you're usually working with 9"-12" blocks and you can get these flat on the ironing board. Also good for bags.
I did use a fusible batt for a baby quilt once. I didn't like it much, because I couldn't fuse it on my table, where I'd laid it out. I didn't like the fact that part of it hung over the edge of the ironing board while I was working. I like my quilt sandwiches to be perfectly flat when I baste them.
I did pull the ironing board up to a table, to help support the quilt at the back, but really felt uncomfortable with the process. I also didn't like the fact that I couldn't pull the quilt top up and reposition it, the way you can with basting spray.
That said, I have friends who love fusible batting. I guess it's a matter of taste.
I'm with CJ - go with the 505 spray. If you have a table that is big enough for your quilt to sit on its a good way to work at a higher surface and not crawl around on the floor.
A friend lets me use her ping pong table for bigger quilts.
Hi -- I have used it but only on purses. I really liked it, but for a large quilt you would really have to iron it a lot. But it was easy to quilt through and wasn't sticky with the fusible. The kind I got wasn't very wide so it would have to be pieced.