I do wish NewYorkCatholic would desist from expounding on matters of which he knows so little.
StuartK, if there's something in my post you object to, please address it specifically. Otherwise I don't know if I said something incorrect, or if you just don't like my conclusions even though they may be correct.
I said Jewish ancestry is not a problem, and that seems to be the consensus of the others on this thread.
Modern-day Judaism, which definitely looks to other sources beyond the Old Testament, makes use of the Talmud, and I have seen the blasphemies in the Talmudic texts myself.
It is also a very common view that there are many ways to be a Jew, not all equally good but still they do not make you "not a Jew." But becoming a Christian does, according to many Jews who have told me this personally and according to the views of many Jewish organizations, make you "not a Jew."
One major example: that State of Israel has various channels through which non-Israeli Jews can visit and obtain citizenship, by referring to their Jewish ancestry. There are various ways this can be ascertained (proof of maternal Jewish lineage being the main one). However being a professing Christian will void any claim of being Jewish, at least for this purpose.
I wonder, but don't know, if professing Islam does the same?
However one can be a liberal Jew, secular Jew, orthodox Jew, reform, conservative ... and in those cases still take advantage of this process.