Ptolemy is hilariously pretentious. Nonetheless, it is a guilty pleasure of many. If the fact that people will snigger behind your back doesn't bother you then go for it.
This name isn't quite as ancient as it used to be. Ptolemy Tompkkins, son of the "New Age" author Peter Tompkins, is now a fairly well-known author in his own right. And in October 2007 the American actress Gretchen Mol and her husband Kip Williams named their son Ptolemy.
Ptolemy was a name used by many Egyptain kings. It is also the name of a character in Jonathan Stroud's Bartimaeus series (the third book is even named Ptolemy's Gate after him).