SEO Powersuite is a bit of a different product. It is not a cloud-based service, but a desktop application, or even a set of desktop applications. Actually the suite contains 4 programs. Combined, they basically provide you with all that you need for your SEO campaigns. It depends whether you like to work with a desktop appilcation or not. If this suits you, you get a full-powered set of software for a one-off fee, without the need for recurring fees, and unlimited number of websites to track. This makes it stand next to Market Samurai and WebCEO though they all have their stronger and weaker points.
SEO Powersuite offers a limited edition that allows you to try out most features. It has limitations as to how many items can be checked /investigated and it doesn't allow you to store the project information, for this you need to buy the full version of either $299 or $699 (the latter for reporting options). Also it is possible to buy the products separate from eachother. So, let's simply discuss the 4 different applications separately, they work fully independant of eachother:
This tool can check out a lot of information, and look out for potential link-partners, based on either keywords or simply by checking out competing URLs. Also you can configure a default link-request form to send to potential link-partners.
You can check out further information and prices on the Link-assistant.com website.