personally I am dissapointed by the temps on my i5 and I am not even using the stock cooler, I am using the arctic freezer pro v2.
As a comparison in same case with same components other than motherboard and cpu.
old overclocked core2duo 6420 with stock fan from 2.16ghz stock to 3ghz. idle temp 27C load temp 49C
new core i5 750 stock clocks with fan as above idle temp low to mid 30s and load temp of low to mid 60s. This is with stuff like linx and prime95 tho so when very stressed. But enough to see I dont have much headroom for overclocking, certianly not as much as my older 6420. Thankfully the i5 is way faster even at stock so there is less of a need. Also the idle temps are dissapointing when you consider that idle voltage on the i5 is 0.8v (lower than my 6420) and it downclocks a LOT on idle to 1.4ghz.
Is entirely possible I got a poor contact from cpu to heatsink but I am not reinstalling it. Agree also on the stock fan, looks tiny compared to the cooler I used and is actually smaller than the stock fan I got with my 6420.
The cpu on its own will overclock to 2.8ghz with all 4 cores loaded and to 3.2ghz with 2 or less cores loaded.