eg the coolers for i7s and i5s.

SPCR tested the Intel stock cooler for the 1366 i7 920 but I suspect that the results are probably fairly typical of any cooler of this type.

I would describe them as semi-quietish at idle. Basically quiet enough to get you through the webbrowsing and whatnot, but they get louder if you actually use your CPU.

Depends on the CPU too. I think <=95W CPUs that are undervolted at stock speeds will be fine; that's how I run all of mine (with 3rd party) but when they were using the OEM cooler, I was pretty impressed.

Since lodestar already posted the SPCR review link, I'll set performance aside and just point out that it is a hassle to install a replacement cooler later if you're not happy with the stock one. It's better to just buy a good one off the bat so you never have to touch it again once it's on.

stock cooler was loudest component till i got hyper 212 evo

For the past 5 years I had been happy with the stock Intel branded cooler on my Core 2 Duo. Silent? No, but by far the quietest thing in my box. Rarely, even under gaming load, ever went above 1krpm.

Just upgraded to an i5-3570 and was appalled to find the heat sink is half the size/mass of the old one. Lowest speed is just over 1krpm and has a "tick" to it (this last may just be bad luck with my sample). Its winter in Canada right now so under load its barely hitting 60C so the fan isn't ramping but I expect when summer comes and the ambients climb it will be an issue so I'm hunting for an alternative right now...

I haven't had any issues with the stock cooler on my i5-3570k. I live in Hawaii and the outside temp rarely gets below 70 and I keep my house at 73 year round. The only time I heard the cooler get loud was when I was running the Intel Burn Tests when I first put together my system. Keep in mind, even though it is somewhat quiet, there are better solutions out there that are much quieter and much better at cooling.