Should I buy a refurbished laptop that came out in 2011?

I'm not familiar with how refurbished computers work, but being that it's refurbished, it might have a different version of the operating system (Window?), so it might actually last, a little longer than a new one, but not by much. That's my guess.

Purchasing a 2011 laptop, in the year 2015, is a bad idea.
The computer I'm using to type this answer, was also purchased (new) in the year 2011. I have used it for 4 years, and I'm now getting a new computer (HP Envy K203tx).
A 2011 laptop probably uses a 2nd generation i7 CPU.
My new Envy will come with a 5th generation i7 CPU.
A 2011 laptop probably uses 1333MHz SODIMM.
My Envy will come with 1600MHz "Low-voltage" RAM.
A 5th generation i7, clocked at the same speed as a 2nd generation i7, will offer much better performance (instruction per cycle is increased), and will consume much less power (lower TDP, longer battery life, less internal heat).

Get the refurbished computer ONLY if the price is incredibly low.
I also won't trust a refurbished computer's internal hardware much.
The manufacturer has replaced the faulty parts of the computer before putting it up as a refurbished product. But the non-faulty parts of the computer have not been replaced and those parts are already 4 years old. Consider the warranty. If the refurbished laptop comes with at least a one year warranty (on-site preferable) and is also priced very attractively, go for it. Otherwise, you're better off getting a 5th generation i5, it will be faster than a second generation i7, will give much longer battery life, won't heat up much, and all the internal parts of the computer will be brand new. Also, if the lenovo you're looking at does not have a dedicated graphics card, intel graphics on 2nd generation i7 is not up to the mark. Intel graphics in a 5th generation i7 or i5 or even i3 is much better.