Tor has been analyzed extensively by cryptographers and security researchers; there is literally a mountain of published research about it. It is operated by an independent organization. I would be more cautious about the Linux kernel, a vastly larger codebase that could and probably does have numerous back doors, than about Tor.
"A proxy server won't work for the same reason a personal server wouldn't work. It's tied to you eventually, either through a paper trail or a packet trail."
Which is why it is below anonymous remailers and Tor on my list. Proxy servers are better than nothing at all.