Introductory Greek texts

I'm teaching first-year Greek (two semesters) to seminary students next
year.  In conversations with various persons who have taught Greek, I have
heard negative reviews of about a dozen textbooks.  One person told me
that Machen is still the best we have.  Does anyone have advice, or,
better yet, a good recommendation for an Introduction to New Testament
Greek textbook?

Philip Graber
Emory University