Lalo Zanelli - former pianist of the Gotan Project - and his sextet gave the evening a clear Tango tinge, but sliding into jazz every now and then, with delicate and intense improvisations.
AudioBoo is a breeze to use and can record for as long as you want. Clearly, the limiting factor is the publishing aspect. While both can publish their clips over GSM or WiFi, you'll most certainly find yourself in a situation when you are trying to push audio up over EDGE, and it can take forever while the iPhone can't do anything else.
You can edit part of the metadata (title, description and tags) once the Boo is published, but not the associated image or the geolocation. The latter reflects the upload geolocation, not the recording location, so be warned.
Nevertheless, it is a lot of fun to use. Checkout AudioBoo's walkthrough on Vimeo to have a feel of its features.
I found a few pictures of the evening on Flickr.