I've been straightening mine a lot lately (read -- wrapping when wet, not blowdrying or ironing) because it's getting too long to do much but wave and I like it long. I also like to give it a break from scrunching and all the product I need to use when it is curly. I am really tired of the scrunched look. It looks so 80s to me.
Does it stay pin straight? of course not. But the longer it is the straighter it is, and without the heat it is pretty frizz free.
Sometimes I add smooth curls with rollers or pincurls.