dob. Mark mentioned something about some galaxies in Delphinus, the Dolphin, that we ought to track down. I opened up chart 16 in Sky Atlas 2000, but there wasn't a galaxy to be found in Delphinus. But, in Uranometria 2000, there are at least a dozen! Using its detailed charts, we were able to star-hop to a few of them, some with surface brightnesses below 13 magnitudes per square arcminute. The galaxies we saw, NGCs 6927, 6928, 6930, and 6944, simply would not have been possible using Sky Atlas 2000.
Uranometria 2000 also has some other uses. Often times, after I've bagged one of my Herschel list objects, I'll notice some nearby objects on the chart that I wasn't originally looking for. I'll then take time out and look to see which of those other objects I can track down. Or, you can simply pick a chart and go for it. One night at the Texas Star Party in 1998 I started on and never left charts 193 and 194, in the heart of the Coma Berenices/Virgo galaxy cluster. I observed and logged more than fifty new galaxies (not including the usual Messiers) that night. It was galaxy-hopping at its finest!
A companion to Uranometria 2000 is the Deep Sky Field Guide to Uranometria 2000. This highly useful guide provides tabular data for virtually all the deep-sky objects found on the charts. The data is tabulated by chart number, and organized by object class (open cluster, planetary nebula, galaxy, etc.). While not purely essential for observing, it provides a wealth of information on virtually anything you want to observe.
So do you really need Uranometria 2000? Maybe not. For one thing, it's a little pricey - about $80.00 for both volumes plus another $50.00 for the field guide. But if you're a visual observer with a moderately large scope, then it will help you discover that there is much more "out there" within the grasp of your eyes and telescope than you ever realized. I can tell you that it did for me. If you own a really big scope, say an 18-inch or larger, I would say that it is essential.
Now the question is, do I need Millennium Star Atlas? Hmmm…