I've spent quite a bit of time with the ESV by now, and it is indeed one of the finest versions available, competing with the NASB for accuracy.
There are indeed plenty of passages where the ESV provides a superior rendition than the NASB. But there are still plenty where the NASB is still superior to the ESV. Either way, Christions should look at either of these two translations I believe.
I'll give one example of the NASB's superiority, John 7:31, ESV "When the Christ appears, will he do more signs than this man has done?", NASB, "When the Christ comes, He will not perform more signs than those which this man has, will He?".
In the ESV, it appears to be an open-ended question. Will he do more signs?? The NASB brings out the truer sense of the Greek construction, that surely he WON'T perform more signs. I guess this is part of the ESV's greater readability, but for this verse I'll take the NASB's accuracy. However there certainly are passages as well where the ESV wins out, so either of these two excellent translations should be bought and read.