Quite simply a superb recording device. The sound quality is, as one of my clients commented, "...better than hearing it in the room!"
It's light enough to fit on the end of a boom (for which you will want the accessory pack with the mic clip adapter/hand grip attachment), and is very quick and simple to use.
I record primarily indoors with the XY stereo mics, and have found that once you get the right balance with the mic gain (and I do this using headphones in the line out) you can get the desired amount of recording volume, while eliminating background noise and all hiss). The closer you can get the voice to the mics, the lower the mic gain needs to be, so a boom and a pop screen might be handy (but are not essential by any means).
Outdoors it's just as good. I have the H2n Accessory Pack, and would say that the mic clip adapter/hand grip and windscreen are a good buy owing to the tremendous mic sensitivity. I have found that I can hear things using the mic and phones that I can't otherwise hear. Again, the mic gain comes in handy when eliminating unwanted background noise and focusing in on just what you want to record.
I bought an additional 8GB SDHC card that gives just under 4 hours of recording at top quality. The included 2GB Kingston SD card is fine if you need less.
As an aside, and this in no way impacts the quality of this fantastic recording device, I found that the free bundled Wavelab LE7 software is a bit of a headache to register, but hey, it's free.
Hell yes, buy it!