The data is packed in the Early Access version (AFAIK the install size isn't going to be 150GB, but I'm not sure if or how much the current size is subject to change; if you were good at 70GB, you'll probably be ok, for now).
The main problem with steam is whether it's actually 150gb or not, if what's entered in the specs is 150, it will only install if you have this amount of space on your disk, hence many of us will have to uninstall games in order to install yours.
