I bought this dictaphone recently in order to assess the difference in quality between my previously used cheaper version and the more expensive models that are on the market.
I can't deny that I was extremely impressed. My old dictaphone had amazing quality and didn't cost too much, I used to be impressed by the amount of breathing that it managed to pick up whilst in use. This takes things to another level, the sound quality is absolutely perfect, there isn't a single sound that passes by this product without being picked up, recorded and saved.
It also has a lot more flash memory than I am used to, meaning that there is no need to immediately remove the files from the handset in order to make space for more.
Another feature that I love is the microphone directionality settings, you can 'aim' the recording power of the mic towards certain people or groups, or just set it to capture every sound in the vicinity. This makes your recording versatile and avoids picking up unwanted sound.
As for interference it doesn't seem to exist at all, the hardware here seems a lot more advances that what I am used to in cheaper models and works well to only capture the things that need to be captures, not the useless pieces of interference which have always been an annoyance.
Overall I advise that those of you considering upgrading to more expensive dictaphones such as this one should make the move as you will undoubtedly be extremely impressed with the improved quality and usability of this.