Being a cheap bastard, I've only ever used a water aspirator (water is fairly plentiful in this city, and free in this building)... all-glass model with built-in backflow preventer (which works well enough that I've never sucked water into the erlenmeyer flask setup to catch such events). Just last night it was pulling a vacuum strong enough to distill our favourite 2-alkene at 118C (very steady vacuum as well - I guess I have a good water supply)... what is that, about 9-10 torr/mmHg? And yes, the water here is icy cold out of the faucet...