Azureus had a share of 3% last year in September but since then it's install rate declined by 30% while µTorrent's install rate nearly tripled.
From the data where the report is based on we further learn that Limewire’s popularity is slowly declining. However, with an install base of almost 18% it is still the P2P application that is installed on most desktop computers. Unfortunately Digital Music News has trouble interpreting their own data, they claim in their press release that it is 36.4%, but that is the market share compared to other P2P clients (shame on you!).Source: Torrent Freak
Apart from this tiny mistake, there are a few more concerns about the usability of the data. For example, install rates do not equal usage. The fact that someone installed a P2P client does not mean that they actually use it. So the report can’t say much about the popularity of a filesharing network or application. Secondly, it could be that Azureus and BitTorrent Mainline are installed on almost an equal number of PCs, but that the BitTorrent mainline client is hardly ever used. For instance, novices may start with the mainline client, but move on to better BitTorrent clients later on. Lastly, the report is based on a sample of people who voluntarily did an online spyware scan, something to think about.
Perhaps an even more important comment on the data collection for this report, uTorrent doesn’t necessarily use the Windows registry. So the real install rate for uTorrent might be even higher. Also, Azureus is a true multi-platform client, whilst this test is only for windows based systems.