I bought this to use with the supplied mini-aerial and was dismayed to read on the side of the box: "In Great Britain, in most cases indoor reception with the rod antenna provided will not be possible." I plugged the thing into my iMac, installed the EyeTV Lite software, and indeed no channels were found.
However, after repositioning the aerial, I did manage to receive all of the Freeview channels available in my area. The quality of the picture is pretty decent, but is dependent upon the aerial's position. For example, it needs to be moved when switching between BBC and ITV channels. The magnet in the base of the aerial greatly aids with this, and I found that attaching it to one of my desktop speakers improved the picture. Even then, the picture and audio are sometimes choppy.
I would definitely recommend upgrading the software to the full version of EyeTV. Apart from the improved features (programme guide, recording, preferences, etc.), it also improves the picture via its deinterlacing option.
Despite the relatively poor reception, I decided to keep the Nanostick for use with my MacBook Pro, turning it into a portable television. Using a static, external aerial would undoubtedly improve the Nanostick's performance, but this is impractical for me and I haven't tried it.