Not bad. I sat their for the Woman in White in March and the seats weren't bad. In fact I am sitting their again on the 29th for the show. Good deal for poor, college students like myself.
The $25 seats aren't that bad if you're on a budget. If you're still on a budget I know broadwaybox.com had some great deals, though I don't know if their still good.
There is no Balcony in the Marquis Theatre, so as far as I am concerned, those seats do not exist.
Now, the last rows in the Mezzanine are however not bad seats, you are a little far away, but the rake/angle makes you feel like you are a little closer.