I liked Girl From Monday, I would recommend that and every other Hal Hartley film I've seen, though my favorites are No Such Thing, Henry Fool, and an arbitrary selection from his pre-Henry filmography (Simple Men, Trust, The Unbelievable Truth).
But yeah, anyway, I've become a major adherent to his work since seeing Amateur last year and would strongly recommend him to anyone looking for some unique contemporary cinema. A lot of people, who are otherwise quite receptive proponents of "indie" flicks seem to be turned off by Hartley, which I don't fully understand. His films are at least as accessible as Jarmusch's (the only director I can think to compare with), and generally a whole lot more intelligent.
So yeah, see The Girl From Monday, and also see No Such Thing and Henry Fool, at the very least.
No Such Thing and 'Girl' are pretty singular, even for Hartley. They're both very minimal, spare films where the actors have to simultaneously embody abstract elements as well as human characters (for example in 'Thing': constructed characters which create the world-through-mass media, which in turn creates the characters they play). Of the two, I'd say 'Thing' is more successful and has a bigger budget, but
everyone else seems to hate it, so what do I know?
Henry Fool is a bit less ambitious than either of the above, but for my money it's Hartley's most enjoyable, the one I keep going back to, and in agregate the best acted of his pictures. And I really love the minimalist soundtracks Hartley composes for his pictures too.
[edit]whoops, guess I didn't really touch specifically on Girl From Monday there. My recomendation is to check out those other two first (unless you have more convenient access to 'Girl') and see how you like 'em.
Also, I'm not sure if you're aware, but I don't think The Girl From Monday is out on dvd yet. Do you know something I don't? (if you do, please tell, I'm interested in buying it).
[etid] Here's a general rank for everything I've seen:
No Such Thing, Henry Fool, Trust, Amateur, Unbelievable Truth, Girl From Monday, Simple Men, Surviving Desire, various short films.