It's not bad for lower than stock voltage, and the stock cooler
Ignoring the onboard graphics instability under load, I pushed to 3.8 with the same voltage - this is a very good chip, and I know for a fact it could go further. If I'd used a separate graphics card, thus disabling the onboard graphics, it probably would have gone to 4.0 - with an aftermarket cooler, even a very cheap one as the i3's put out very little heat, I could have gone further, as I could with better RAM.
But, then I sat down and remembered the aim of this build was a cheap internet machine...
For reference, maximum temperatures after a full 12 hours of Linpack were 65C - this is way above any other load anyone can put on a processor, and while running CrystalMark's CPU benches it didn't break 50C. I love i3.