I recently used the H6 for field recording a documentary and I highly recommend it.
The H4N is a good old standby, but it is outdated and making adjustments on the fly can be cumbersome.
Update: I got a great deal on an H5 and compared it to my buddy's H6. If you don't need a color interface and four track recording out of the box, the H5 is the way to go. I like the XY the H5 comes with a wee bit better as well.
