I think the UHT processes must have really improved. I grew up with pasteurized milk in the UK and when I spent a couple of years in France in my early teens I found the taste of UHT seriously gross. However, since moving to Spain a couple of years ago I've found that it pretty much tastes the same as pasteurized milk these days, maybe a tiny bit sweeter.

Interestingly, the pasteurized milk available here in Spain tastes way less like UK pasteurized milk than the UHT stuff. Also curdles after like 3 days of being opened. I guess there are various processes for both pasteurized and UHT.