This is with the OS X 2007-12-20-nightly_1.0_branch, Leopard, Macbook.
Some stuff I noticed, but I don't have much time to test so just letting you know:
1. Miro identified itself as libtorrent, or is being detected as such, see http://tangerine.quickshareit.com/share/afbeelding2b05b8.png
2. It took at least 5 minutes before Miro actually started downloading data for torrent from the screenshot.
3. Paused the torrent. Clicked the 'clear completed and failed downloads' bar. I think Miro removed the paused download from the dowloads view.
4. The preallocated data remains in incomplete downloads when I removed a download that was in progress.
4. Initiated download, started redownloading when i quit miro while the torrent download was in progress. It started over. However, closing my laptop lid and reopening worked fine torrent-resuming-wise.