Just got the H4n yesterday.
Improvements have definitely been made over the previous H4 and even H2.
1. Improved, quieter pre amps.
2. Input gain works as it should. It seems that the pre amps were wired properly on the board, so input control does in fact raise and lower the gain input as it should, which can prevent clipping.
3. Solid bod construction. Doesn't feel like a piece of puffed plastic.
4. Much larger and brighter screen. Very easy to read.
5. Control layout is much improved, and access to items in the menu is much easier as well.
6. Built in limiters seem to function better and are more responsive.
7. Rotatable mic capsules are a welcome addition.
8. 1/8 mic input. I wouldn't need it myself, but it's nice to have.
9. Ability to use built in mics along with dual XLR or 1/8 mic input. Very nice, and very useful for my recording needs.
Shortcomings that I have noticed so far.
1. Mic elements are a bit thin, and too sensitive. Their alright for a sub $400 recorder, but just an observation.
2. XLR inputs are still noisy. They are much improved over the H4, but still a tad noisy.
3. No external L/M/H Gain control. I liked this as an extra measure to prevent clipped audio. Just have to be more careful during setup is all.
4. Not able to control L/R XLR channels independently. At least not that I have been able to see so far. You are able to control the oboard mic and XLR inputs separately while in 4 Channel record mode. But you don't have access to control either left or right XLR input level gain.
All in all I am very happy with what I have seen so far form the H4n. Just have to put it through some hard testing to see if it's a keeper for me. Mind you this is compared to my Edirol R44 for multi track recording.