John,
Thanks for bringing up this excellent and pertinent (at least to me) topic :-).
Due to physical limitations, up to this time I've sent my quilts out to a professional longarm quilter. Due to financial constraints, I've only had them do one of the simplest all over patterns. While I have been delighted with getting a finished quilt, I have also known that the end result was not optimum. Given the quality of my patchwork, that did not bother me too much, though this issue was always in the back of my mind.
Yet, I have not worked in a vacuum. I've taken a glance at a book called something like, "Quilting Makes the Quilt" at a book store and that book really demonstrates that the actual quilting can make a great difference in the final look of the quilt -- dramatically so. I've also seen beautiful quilting at shows, in magazines and other books. I bought some of those quilting books, even though it is unlikely that I'll actually do any quilting, except on small wall hangings.
I've been seriously considering making a Dear Jane (DJ) or Dear Hannah (DH) quilt (or some other complex sampler quilt). Quilts like these need a bigger commitment than quilts that I have made in the past. It seems to me that if I do make one of these quilts, then it would deserve more consideration regarding the quilting than I've done in the past. Given that all of the pieced blocks are different, then such quilts would ideally have each block quilted separately in a manner that enhanced that individual block. This would cost considerably more than the simple, overall quilting designs that I've previously had done on my quilts and needs to be considered in the funding of the project.
Please don't get me wrong. I don't mean to imply that simpler pieced quilts don't also deserve beautiful quilting -- one only needs to look at some of the gorgeous wholecloth quilts to debunk that :-). Personally, I find great beauty in wholecloth and simple patchwork quilts. I only mean that if one puts so much time and effort into the patchwork side of a quilt, then it would seem a shame to not use the same level of consideration with the quilting.
Regarding the crossing of seams when quilting, I'm far from an expert :-) and I tend to break the "rules". I take my quilting perspective from applique. There are times when applique does not cross block lines and others in which it does. It all depends upon the desired effect. If a patchwork quilt's design is best enhanced by staying within the seam lines wnen quilting -- great. On the other hand if its design is better enhanced by sewing over seam lines, then IMHO that's the best way. Given that applique is more pronounced than a quilt thread, I do think that one would have to be careful in the way quilting crosses seam lines. I also agree that an overall quilt design is most probably not the best design for a quilt, but it may be the quilter's only option at the time due to monetary, time and other constraints.
BTW, while this is "critcism", it is "constructive criticism". This is how we improve our work so I want to thank you again for your comments.
Bev in TX