They are excellent! Nearly all nectarines are excellent though … its a low bar. The Summer Beauts have a more perfumed/creamy flavor than the Mericrest which I like a bit more, but they are a bit more mushy in the flesh which I like less. I think there is something very weak about the Mericrest skin, not only is it getting more spotting and rot, the birds and the fruit flies are all over it whereas the Summer Beaut just has a couple pecked fruits on it. Some micro-cracks have formed in the rain and then the fruit flies can swarm in to that.
Next spring I will probably topwork some other nectarine like Summer Beaut on to the Mericrest. Those in less hot-n-humid climates can probably still do very well with Mericrest, but its not making it for me any more. Often when its ripening there is no rain, and its much better those years, but I want varieties that are good every year (or, that are really unique so they are worth suffering through).