MIGRATION/UPGRADES & STABILITY VS PLAYGROUND ZONE. I appreciate what you're saying and yes upgrading could be easier - but the benefit of the way Rails does it now, is that uptake is significantly higher, because it is practically pushed on you. I think I prefer this because it helps keep Rails cutting edge (one of the reasons I choose Rails over other frameworks). Maybe I'll change my mind once I've got a few apps that need upgrading - then again maybe not, I've always preferred redoing things from scratch than upgrading/patching things anyway (with app-powered sites such as wordpress/vbulletin - I would redo the customisations from scratch for every major upgrade - but happy to patch minor updates).
PUBLIC/PRIVATE/PLUGIN APIS. I don't really have an opinion on this.
RAILS/MERB MERGE WAS A MISTAKE. I remember when I first started researching web frameworks, the Merb and Rails split worried me - as I thought it would end up in two factions (two frameworks basically aiming for the same thing) and would split the community. So the merge did two things (for me anyway) showed me the community is united (and not affected by egos), and made me feel better about coming to Ruby (instead of going with a framework in another language).
TECHNICAL DEBTS. Again I don't really have an opinion on this being a relative newcomer - but I guess many people would disagree.
KEEP THE COST OF ENTRY LEVEL LOW. This one I think I am qualified to comment on :D I didn't choose Rails because it was 'easy' to get into (although it is, because it is written in Ruby). I choose Rails because it was the best web framework. If people want wordpress-ease, they should use wordpress - a web framework is completely different to an off-the-shelf app which is designed for one main purpose, even if with some leeway for customisation. I left off-the-shelf packages for Rails because I hated being restricted by them, and I was prepared to learn to program to use Rails. To my surprise, learning Ruby and Rails was much easier than learning say PHP and CakePHP (which I tried briefly). Also, I believe anyone serious about learning Ruby and Rails, can easily, in about 3 to 4 months by following this guide: http://astonj.com/tech/best-way-to-learn-ruby-rails/
DOCUMENTATION I have to disagree - I love the Rails Guides, I've been reading them from start to finish on my Kindle (currently half way through Digging Deeper). Of course maybe like almost anything they could be better, but I disagree that they're "far from great". Try working with a forum app where documentation is next to non-existent lol.
SUMMARY. I came to Rails because I wanted a cutting edge web framework, one that was written in a clean, modern language - and that's what will keep me here. I'm aware and happy to continue learning and keeping myself up to date to stay current. What I don't want is a framework to lag behind others - that would very quickly make me think about jumping ship... and I reckon a large majority of others think the same too.