I really like the attachment option, I use it as much as possible because its just simple to use... however there are times when I just upload an image to display in the thread then use the [IMG]attachment url[/IMG] to show it fill size but then I see both the thumbnail and the large image, and in some cases many thumbnails and images (kind of anoying)
I would love an option that when we upload attachments we can select not to have inline thumbnail generation for that particular post etc.
that would be really handy imo