Short answer regarding the forms is that there has been much talk of "wizard" functionality, but I don't know if there is a clear plan on how to do that.
Oh. Wizard is designed and will be coded within, hm, seven days? We will employ a cache_form table to store forms and submitted data as opposed to the current situation where every multistep form function itself needs to store its submitted data in session/hidden whatever. The builder functions will get the $form_values still but they do not need to provide hidden fields to store the information in. What's more, they can't do that because form_builder will *not* get the posted information -- every step is an invidual form and the submit handler gets the array of $form_values keyed by the steps. This neatly solves all possible problems because there are no special cases, every form , #multistep or not, starts its lifecycle as a nonsubmitted form. Most problems currently --validation,checkboxes,whatnot-- arises from the fact that every step begins its life with the burden of the previous POST. For JS guys, the plans are that we will make it possible for JS code to basically do a form_alter, store results in the aforementioned cache_form table and send back the themed form element. I am a bit unsure of who/how will produce the JS but the PHP scaffolding will be in place, soon. Regards, NK