Honestly, while I understand the decision, CI3 was a moving target for most of the development period. It may have been more stable in the last couple of years than the development branches of most PHP frameworks, but it wasn't truly stable until the session branch was merged.
I've been focusing most of my available development time for Bonfire on CI3 compatibility since RC1 was announced. I released the first version of Bonfire with any level of real CI3 support 10 days ago. Now, I'm looking at moving the platform to fully support CI3 (with minimal CI2 support) in just over 6 months. This means that I have to spend all of my available development time on CI3 compatibility, including some time that otherwise would not have been spent on Bonfire at all.
Realistically, the documented changes are not terribly difficult to deal with, though I ran into at least one that drove me to create a compatibility function to get over the issues until I have time to rewrite a couple of libraries. The undocumented changes and other unknowns are a nightmare, though.
At this point, I know that most of Bonfire works fine under CI3 (with the changes I pushed to Github this morning). I have no idea where I should expect problems to appear as I start testing not only Bonfire but my entire site. The issues people have been reporting with set_value() and the form_validation library are certainly a concern, and the overhaul of the database libraries could cause any number of subtle, difficult-to-trace errors.
