Very strong idea, and it is apparent that a lot of thought and work has went into this already. Functionally, the reports and questions etc seem great! In general, it feels a little bit overwhelming at first (a lot of info on each page, but some of this feeling may just be minor design cues like font choice, size, colors, margins, padding, etc). It was difficult to know where to start or what to look at first on some pages.
A few constructive comments on the marketing side of the site. The product itself looks well-thought-out in a good market niche.
- General look and feel
It's professional but a little lacking in whitespace, especially since you've chosen such heavily saturated colours.
- Home page
The three key points at the top aren't as eyecatching as they ought to be. Oddly, they work better in IE without the drop shadow (which appears to shift the block visually upwards away from the dynamic content and into the header). shifting it ~10-20px down the page might help a bit, as might rollovers if you want most users to click to learn more.
My attention gets drawn away from the text on the left. Possibly a box (with curved edges and ideally vertical dimensions to match the slides might help) and/or a pastel background colour might help here.
The animated slides are effective, but possibly a slightly reduced size would give you the scope to make other changes
(most of the graphs would still be clear at much smaller resolutions)
I'd revise the "Secure" text - developers might be interested in knowing that passwords are securely hashed, but Joe Manager just wants to know that it's "password protected and private" and even more importantly "you decide who can see what level of feedback". Customer permissions sound like they could be an important feature depending on the level of openness within the company. Some companies might be comfortable with everyone knowing exactly how each colleague voted for each peer, whilst others might want to anonymise all the votes even to management analysing the results.
Minor point, but there should be an apostrophe in the possessive "each other's" (there seems to be some consensus amongst pedants that each others' is incorrect as both "each" and "other" are singular")
- About Peerleaf page.
Text is a little overwhelming. Stick "Security", "Requirements" and "Privacy" at the bottom of the sidebar (or on a separate FAQ page) to keep the flow of the page about the core benefits and use cases of the product. Your flowchart looks better above the fold too
On a more concrete note, the green and blue tabs at the top seem inconsistent, compare https://peerleaf.com/Report/1 to https://peerleaf.com/About Shouldn't the demo tab be blue when you're on the demo page?