Bits on Wheels, despite the fact that it's a 100% native client, was too slow and RAM-hungry for my taste. Transmission on the other hand could probably be called the µTorrent of Mac OS X. And even though it's possible to run µTorrent in Mac OS X, it can't be considered a competitor as it has to be run through an emulator. Transmission is less than a MB in size and takes up less memory than any other Mac BitTorrent client.
The last 100% stable release of Transmission is 0.6.1. The latest Beta release is 0.7-svn (993). It is the beta version I'm all excited about as it includes a number of feature improvements/additions and visual enhancements, that make Transmission truly great.
The first thing I noticed was that the blue, mechanical-looking icon that is seen in version 0.6 is gone. It has been replaced by a much nicer looking one. I'm not sure exactly what it is, but looks like a lever in a double-arrow shaped frame. Unique and attractive.
The dock icon badges that display the upload and download speeds have new colours. Instead of fully coloured blue and green backgrounds, they now have grey ones with coloured outlines. This looks a lot classier, and not dissimilar to Xtorrent's black dock icon badge.
Don't get the impression that the improvements made to Transmission are limited to eye candy. There's new stuff under the hood too.
Speed Limit Mode
For starters, there's now a way to have Transmission automatically limit download speeds at certain times of the day. For example, if you don't want your browsing speed hindered by your torrents, you could limit it during the day, when you are at your desk. I've set it to limit my upload and download speeds to 10k between 11 AM and 3 PM, the hours I'm usually working.
A feature I was very excited about when I reviewed Xtorrent last month was Autodownload, an option, if activated would automatically copy .torrent files on the desktop to Xtorrent's support folder and start downloading them. This makes torrenting as easy as downloading files via HTTP, as all the popular Mac browsers save files to the desktop by default. Transmission now has this ability too!
Last, but not least, is a Finder-like feature that lets you sort torrents according to their status or by entering a keyword. This could save you some time if you download a lot of torrents at once.
One lingering drawback is that Transmission is still based on the Open Source libtransmission package that is banned by many prominent trackers because of the way it repeatedly "hammers" them (ie. doesn't obey announce intervals). Its stat reporting has also been regarded as poor. Let's hope something is done about this. Either libtransmission should be improved or the developers should switch to using libtorrent instead.
Overall, Transmission 0.7 Beta has this polish that I've only seen in Shareware Mac apps like Acquisition and Disco. Best of all, this excellent piece of software is Open Source and available to anybody for $0.00!