Looks good overall.
Here's my thoughts:
1) A Small inconsistency (well maybe not so small)
"All accounts include $10.00 in free credit! That's up to 30 days for free! Signup now →"
"We're changing the way your business handles calls – all for a mere $5/month per number."
Is it $10/Month? or $5/Month?
2) The Features page
a) It's really wordy. TLDNR
b) Make the get started with a 30 day trial bigger and more prominent (maybe center it). That's your call to action so make it pop.
c) The footer is slightly confusing. If you're going for non-tech savvy people, don't have things like "@voicendo" as the link to twitter. Just say Twitter. People who don't use twitter will be confused. Also, the popover box for twitter loaded noticeably slowly the first time. I'm not sure it's necessary in the first place and I would get rid of it and just link straight to your account in a new window.
3) The pricing / signup page
a) get rid of the cancel button. It's working against you and really does nothing that's not already on the page.
b) Ohhhhhh this page explains the problem I was having where $10 = 1 month but $5 also = one month. That needs to definitely be re-worded. While I just figured it out from your text, it's still not hitting me in the face.
4) Knowledge base
a) I recommend you seed this with anticipated questions.
5) The front page
a) the grey text is hard to read. It's very close to the background color.
b) Again, Too wordy. I almost think you don't need descriptions. Your headings are pretty self explanatory for the most part (maybe).
Good Luck!