Hey mister k, Ken here from appMobi. I just wanted to chime in on a couple points.
I am new to C2. Seems like an amazing 2D engine. I have dreams of publishing to iOS, Android, Windows phone 8 and Chrome / Google play Store.
You are totally able to do this today no matter what service you go with. The different services let you build for different stores so you will have to make sure the service you select allows you to build and deploy to the stores you want. Here at appMobi you can build for iOS, Android, Amazon, Nook, Win8, Chrome, Facebook. I worked on a game that is deployed to all of these (except win8 as it was not in existence when we built the game).
Yet, reading the forums on problems and bugs with appmobi and cocoonjs, seems like its a work in progress. I don't want to master this great game engine only to be confronted with publishing issues after paying for dev licenses.
I'm willing to bet any service will continue to be a "work in progress" as the industry changes so rapidly. What it was 6mo ago is not what it is today. So any service will continue to evolve, improve and continue to be a work in progress. My advice is to stay away from the ones that aren't :)
As for publishing issue, with any rapidly evolving technology there will be bugs that crop up. However I think you will find that the support is there and they are usually resolved fairly rapidly.
The biggest thing you can do as a developer regardless of what build service you use is to design the game with mobile in mind and don't assume you can just port a desktop browser game into a high performance mobile game. For instance, you have to be a bit more conscience about the size of your image and sound files and not load up your game with 200 large sprites and 75 different sound effect files.
Please would some of you tell me i have no reasons to be cautious.
My personal opinion is you don't have anything to be cautious about, just be mindful of the differences between desktop and mobile and START SMALL. Don't jump in and expect to make the next super involved mega game. Heck even if it's a breakout clone. This way you will learn the technologies, find any hurdles and if you run into bugs report them. We're here and listening :) And if you do go the appMobi route and ever need any help. Just PM or email me email@example.com. I'm more then happy to help.