I don't know whether or not it's the best or not because I'm not 80, I don't have any numbers at 80, and any numbers pre-80 are 100% worthless and should not be even payed attention to. However, I can give you MY three unholy specs.
Leveling: http://www.wowhead.com/?talent=jfVMVZZfMhI0fkxcq0csut
Unholy DPS: http://www.wowhead.com/?talent=jfVMVZZfMhI0ckgcq0csut
Unholy Tanking: http://www.wowhead.com/?talent=j0xMZGx0zZfgGI00oMeoocsut
Now the tanking one, I'll be honest, I just threw that together for this post, so I haven't spent a lot of time refining it.