Actually, I prefer to use the torrent client Vuze (formerly Azureus), because it has a very effective built-in search engine that aggregates (combines) several popular torrent search engines - several of the better sites - and ranks search results by "health", which is a combination of seed/peer ratio, age, etc. It's simple enough for my mother-in-law to use easily, but robust enough to suffice in most cases. And most importantly, it has native support for Linux-based operating systems

. It has built-in support for all the sites you listed above, among others. I don't care for any one website personally, because they all seem to lack some aspect or another. Aggregation for the win!
The client also supports the most popular forms of encryption, and can be finely-tuned for the torrenter who would prefer not to be throttled by the more greedy ISPs

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P.S.
If you REALLY want to torrent quickly and effectively, you should look into some of the private torrent trackers available. I can't list them by name, but you should be able to find them if you poke around a bit

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