...it really means it! I tried to install on a machine with 1gb of ram over the weekend. No, I'm not planning on leaving it that way. I just want to start with some prep and I'll be buying ram later.
Turns out, when you have shared memory for your video card it takes up enough that ESXi won't even install. Yep, even cutting it down to 64mb wasn't enough. I found a note on a forum where someone trimmed it down from 32mb to 16mb shared and it worked.
So beware! For as "light" as it supposedly is it won't even think about working in anything less than 1gb of ram.