actually shu can have good interesting taste. Personally, I'm always looking for natural (as in not infused) aged nuo flavour shu.
To my understanding it may not be from expensive grade shu. Normally it can start developing this flavor around 5 years stored. I have some 23 years old shu bricks that have this flavor. My parents got them from China at scam prices for what I believe low grade material. But they come with certificates (unless IMHO). There's even 4 square bricks that are 30+ years old.
First 3 steeps, you get slight bitter taste with good consistency. Very smooth. After that you get the rich nuo flavor with mild sweetness, normally lasts till steep 7-8. Then the nuo flavor mellow and the sweetness become that from rock sugar.
Actually I find aged shu (even better if it's aged lao cha tuo) is better appreciated if u cook it with iron pot or stainless steel. Learned this from China forums. The flavor is better and most of the time is sweeter.
This can even make US$2 semi-aged shu brick drinkable, which it'll taste horrible if you brew/steep. Of course I'm speaking in term of my family taste for shu. Weather if it suits you, is another matter