I'm just going to hit the bad parts, so forgive the apparent pessimism. :)
The signup process is miserable. There's no reason to have it broken into so many steps. And damnit, after that many steps, why do I have to confirm my account via email and click a "Oh, gee, thanks. Now continue to your real account." No confirmation at all. Take me straight to my account.
Do you really need my phone number for registration ? Not a real question. Answer: NO.
Password length restriction ? Seriously ? My password isn't even that secure and I had to trim it for your guys' site. That's absurd and there's no valid excuse, no matter how plausible.
Six steps to schedule a meeting ? Not to mention the processes of each individual step -- the time selector is severely irritating; why do I have to make three conscious decisions per hour I want to select ? (First, what I click. Second, the hour. [and there's a moment of wait, is this AM/PM where maybe I cancel the click, change the AM/PM, then back] And finally, choosing AM/PM if I haven't already done so.) Just make it one nice big long list. Maybe if you want, select the hour and minutes separately.
Basically what I feel is that the UI is trying to present ALL of the features you provide without a clear understanding of how they're broken down. In your video, you present the tremendously arrogant tone of "everything else sucks, and damnit, we kick their ass" -- which is awesome!- but then I get into the product and it feels boring, bloated. Feels like a some old strung-out dude wearing ripped skinnies and a deep v-neck.
Ok, actually, it's nothing like that. That was a lie -- just that last part I mean. Skinnies rock. You should all wear skinnies.
I'll keep an eye on the product because I'm interested. Just try to embrace consistently the attitude you put forward in the video. Make sure the product truly fits that because then you've got something pretty cool. :)