With Drupal 7 now released, and a lot of thought going out about how it might spread, I thought I would share one plan I have.
As a freelance consultant, I tend to do a lot of work on the simpler drupal sites. Some of my jobs are on relatively bigger sites, but some are quite small. Some only need a handful of contrib modules.
I have one client who provides simple sites for small businesses, and he hosts them all on a godaddy account. Because this client doesn't touch code but is a decent site builder, D7 has a lot to offer for him. I offered to upgrade a copy of one of his client's sites on my dime and let him play with it. Typically his sites use contrib modules ranging from token to nothing more elaborate than Views. No panels or services or ubercarts here. A few don't even have CCK and Views, and most have no custom code. That way we can see both if it is reliable on these simpler sites, and he can see all the new features it has (and get addicted?). Hopefully he will decide he wants his new clients on it, and maybe we also move the old ones. Seems like a good first step for pushing the spread of D7.
Probably one of the bigger limits will be whether the theme we used has been upgraded. He does a lot of searching to choose off-the-shelf themes that only require maybe a changing of a few colors. But a number of the sites have Acquia themes, and I'm hoping that they have been quick to update.
Personally I have only barely begun to dig into D7. I hope to pick up a print copy of Drupal Pro Development at the release party tomorrow night, but the above plan doesn't require any knowledge of the APIs. And if it pans out, it will certainly push me to start digging in in more detail.
PS - I noticed that the D7 distribution is almost twice the size of D6. I don't see this as a big problem, but I'm wondering if there is a specific reason - some change in philosophy, or a specific component, that is driving this?

Comments
Much of the extra weight is
Much of the extra weight is test files, and the inclusion of many new modules such as Field modules, Field UI, and Field SQL Storage, imagecache, etc. Somewhere someone has a list of about 70 contrib modules have had their functionality moved into core.
A few great resources
A few great resources are:
Sala kahle,
Grant