Even though I'm sure everyone here will say it is junk, I have a Craftsman digital level that has worked great for me. I find the digital gauge to be much more accurate than a bubble in liquid. I like to be able to see exact degrees. Bad for someone with OCD because you can never get things perfect.
http://www.sears.com/shc/s/p_10153_12605_00948293000P
I believe there is also a 48" version also.
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When you buy it, stick it against the steel column in the store aisle and note how out of plumb the column is. Turn the level around and see if the bubble is in the same spot. If is the same, then the level is good. If not, the vial is off.