Hello grad students of /sci/,

Undergrad fag here. Have to take my GRE this year - will most likely take subject tests as well because CE major. Is it as easy as people say, assuming the SAT (as well as all of undergrad in general) is was piss-easy for me?
I saw that now one can take the general test online with like two day advance registration, so I was thinking I'd just bang it out over the weekend. Should I actually prepare for it or just go in? Will most schools care if I do end up taking it more than once?
As an aside, are the math/physics/cs subject tests much harder?

plz no bully