My pub bike has a super cheap as chips headset its proper nasty but as its new and the bearings are smooth and the steering is smooth and effortless and has no play in the steer. Its the same as any other headset. In a blind test how would tell otherwise?
But it doesn't have the best sealing so I know it won't stay like that for long. Used have a FSA orbit some thing rather which had far better sealing and only cost something like £35 RRP the bearings in that lasted several muddy winters. When they eventually worn out I popped them out and put some new ones in. 10 mins later I was back on my bike having fun.
Sorry I missed the part about good quality bearings in my original post. obviously if you get a headset with bearing made of cheese then it wont last long even with good sealing but good after market bearings can be had for £10, much less than then offset of buying an expensive headset. I've not had any issues with the bearing life in headsets costing around £30 ish they've stayed smooth and notch free for ages.