I've not had much success with Conti tyres. Far to difficult to get on my rims.
Don't know how good the new GP4000 are but I've used GP3000 in the past and was less than impressed. They pick up cuts far too easily. Fairly small cuts mind, and easy to superglue, but not really what you expect from a brand new tyre. The rear is now through to the canvas after only 500 or so miles after I had to get on the brakes pretty sharpish to avoid a car.
Got some Conti Ultra Sports on the commuter (got them free from Planet X after I had to send some wheels back for a rebuild) and although they were fine for the first 100 or so miles they are now cutting and puncturing at an alarming rate.
The best tyre I've used by a long long way have been Vredestein Fortezza Tricomp. I'm on the second pair on the good bike and they're brilliant. Not punctured yet (fingers crossed), no cuts, feel really supple on the road, grippy as a really grippy thing on a grippy day even in the wet, and they last for ages.