That would give you only 800MB (about 20%) free RAM under maximum usage. That in and of itself isn't a problem, but I'd be concerned that it wouldn't take that much extra usage to hit the limit. And without a pagefile it's a hard limit that will cause your system to start seizing up.
I'd personally be more comfortable with a 50% or larger safety margin.
I think the OS "preemptively" swaps some RAM out when a certain "threshold" usage is reached. Moreover, when disabled completely, the system might just crash. Therefore I wouldn't disable it completely unless you have even more RAM. Even I keep a small 512MB swap on my 8GB machine, worst case scenario: it won't be used.
I have the pagefile disabled completely and the system works perfectly well without it. There's no need for a pagefile if you have enough RAM. I have 12GB of RAM and rarely use more than half of it.
But the penalty for running out of memory is severe - without a pagefile there's no place to "swap" RAM to - when you run out, you're basically hosed. The system will stop working until you shut down enough programs to free up some memory. (Windows 7 is actually pretty robust - in my experience it doesn't crash, it just stops until you kill something).
That's why I think a 20% safety margin might be cutting it a little close.
^Same. I have 6GB of ram and the system idles at about 950MB usage and even if I have plenty of apps open, usage doesn't go over 3GB really...so I have pagefile disabled and the system works fine, never had any crash or issues. Since I have a tiny 80GB SSD, a giant 6GB pagefile is a space hogger for me.