Here's a summary of the changes I made:
1) html::specialchars --> html::chars
2) ORM::orderby() -> ORM::order_by()
3) ORM::where() now takes 3 parameters including a comparator. So
ORM::where("a", $b) is now ORM::where("a", "=", $b) and the middle
value can be any comparator.
4) ORM::$loaded --> ORM::loaded()
5) Database::instance() --> db::build() (and there are some other
subtle differences, like now you always call execute() at the end
of the chain)
6) form::close() and form::close_fieldset() are now gone. Use
</form> and </fieldset> respectively.
7) Controller::$input is gone. Use Input::instance() instead.
I've done very rudimentary testing so far.
We no longer need the install() function for installs that only set
the module version number. Same for upgrade(). Do a general cleanup
of all installers and remove the ones that are no longer necessary.