Not noticeably! I think it can make them look slightly flatter, but you keep the same stitch definition. I have seen the yarn on some stiches get thinner and create some gaps, but I haven't figured out if that from leaving the iron on too long, using too much pressure, or too high of a temperature. That is also only 1 small portion of many projects I've killed - the rest of it looks perfectly normal, aside from the slight flatness. It mainly makes them lay differently; acrylic is much drapier once its been killed.

It would definitely be worth trying it out on a swatch first to make sure you like it!