I belive that the thermal sensors on the Koolance`s are above the waterblock, which is a less that ideal way to get the temps. And so, to a degree, the temp readings are a bit off. If the thermal probe was on the underside of the block, near the processors core, there would be a very good chance that the temps would be nearer the 40*c ~+ range. Although having said that, thats still more than good enough.
If i was to buy a watercooling kit, i would not get the Koolance, any varient. But thats because it doesnt offer the performance that i`d need to justify the cost. I already get 41*c load with air cooling, silent air cooling i might add, so i`d need something that`d drop the temps to <35*c to make the upgrade worth while. But thats just me.
The EXOS is a good kit however. A very well performing kit for WCing n00bs and "amatuer" OCers alike. But for pure performance in temps, something a little better would be required. For someone requiring something a little better than the Koolance`s, then the Asetek WaterChill range is ideal.