Test this if you're curious what it will be like for YOUR application, YOUR audience, and YOUR demo implementation.
To the extent I am capable of commenting publicly on this, I have not ever seen solid numbers which make gradual engagement (technical term for what you're talking about) look like a big win for the company, and to the extent I have seen numbers on gradual engagement, it has been the opposite of a win.
The only numbers I can comment on publicly are the gradual engagement test for BCC. That was my worst Product idea ever, hands down. It 10xed customer support costs because users expected their accounts to magically work (even when, e.g., accessing from home and school and why did your computer delete my cards you just ruined Halloween for my class you monster). The conversion rate for guest accounts to paying accounts was 2. Not two percent. Two accounts ever, in six months, actually saved their email addresses and then, some time later, paid for the software. (This was at least partially because I did not roadblock users at any point and e.g. ask for an email address with a greyed-out Skip option, which is a virtual necessity to get gradual engagement to work. #microUXtip) I have no email addresses for guest accounts nor permission to contact them, something which I have in abundance for trial accounts, and I can tell you that is worth a good deal of money over the long run.
Optimizely and Stripe are, indeed, the two YC companies that I can think of which do gradual engagement. The mafia are very generous with what they know, have an active mailing list, and are universally capable of knocking out a gradual-engagement enabled account system within a week or two. What does this suggest to you as to internal sentiments regarding gradual engagement?
If you want to do something like this, use a post-signup fully capable account for a product tour. Product tours, as compared to gradual engagement, have a) vastly easier UX problems to resolve and b) empirically are full of win. That video I have about the first run experience explains this in a lot of detail.
P.S. Global endorsement of everything btilly says on this thread.