Is this the best place to view projected difficulty?

http://www.alloscomp.com/bitcoin/calculator

I've seen other sites with much lower projections and just wondering what the most reliable is.

Also, after inputting hash speed on the link above, what does row #4 in column #1 mean "this diff (est)"; I don't understand what this is referring to when row #2 is labeled "per Week", and both are contained under the header "This Difficulty". Clarification on this would be great...

I haven't paid close attention to the difficulty jumps, but this site seems to over-estimate from what I remember on the last increase.