I personally don’t use nor endorse the use of Limewire but I have *a lot* of Windows users asking me about Limewire when I install Ubuntu on their machines.
If you want Limewire and you’ve recently switched to Ubuntu, I suggest you take a look at FrostWire. FrostWire is a fork of LimeWire and has better integration into Ubuntu, doesn’t have annoying advertisements like LimeWire and generally works out of the box after installation.
FrostWire now uses Azureus code for downloading torrents. Azureus, to me, is extremely slow and not worth using just to download torrents. So, if you are looking to download torrent content, I suggest you use Transmission, the bittorrent client that is installed in Ubuntu by default and I personally use.
Other than that, happy file sharing!