Alright, yesterday... I was considering the purchase of Market Samurai. I downloaded the trial, had a play around with it, and it looked like a pretty valuable tool to have. Only downfall - it costs $147 to purchase. If you sign up to the mailing list, and order within 7 days of having done so, it costs $97.
Market Samurai offers dozens of tools, including a keyword researcher (which you can use even after the 12-day evaluation period is over), competition analysis, a SERP tracker, a link finder, and a little bit more on the side. The most valuable is the competition analysis, which quickly finds out detailed information on the top 10 sites on Google for your targeted keyword (including PR, how many links the page has, how many links the domain has, how old the domain is, on-page optimization, and again - a bit more).
But... Yes, there is a but...
I found a free tool which is going to stop me from purchasing Market Samurai. Niche Market Finder is another competition analysis tool, which offers nearly as many features as Market Samurai. The good news is that a) it is faster and easier to use b) it offers everything that you need.
I highly recommend this tool.