I've used Unison on the 15 day trial and have to say that it is by far the best newsgroup reader for people who want to download things from newsgroups. By far.

However, when you're dealing with what are typically very many posts (some groups containing nearly a million posts) Unison just grinds to a halt. I realise this is a huge amount of data, but its this lack of performance that is stopping me from buying Unison. The thread caches it creates are also absolutely huge (many GBs on my machine) - again, not sure if there is anything that can be done about this due to how much data is being thrown around.