My past 2 phones have been pentile amoled, and I can certainly spot one immediately. Even the galaxy nexus is still slightly noticeable, although it's marginal and you really have to be looking for it as it is quite high res. Some colors fringe more than others, a single pixel red horizontal line for example will look more like a dotted line, whereas a blue line will look fine.
However I can also easily spot an lcd a mile away because the blacks are never black. My iPad3 vs Lumia:
With the Lumia, the black of the bezel is the same as the black of the screen, not so with the iPad3.
There is a trade-off for pentile amoled and also RGB lcd, each has a distinct disadvantage compared to the other, and for my chosen OS (wp7) black blacks are more important for me.
I look forward to 300ppi RGB stripe amoled displays, which will be awesome.