This is my first time reviewing anything in any depth, but as the director of a start-up, all volunteer non-profit, I discovered J2XML at a desperate time. Our J1.5 site was mercilessly hacked and needed to migrate to get back online. J2XML was the only product we could find (and afford), so we decided to test it out.
I was skeptical. I've used highly rated free apps, most fail to deliver. Those that do often don't do so uniformly. I was THRILLED when it turned out J2XML was a rare exceptional exception. Kudos Eshiol(?)... no, just looked it up - Kudos, Helios Ciancio!
In short, J2XML made migration of content from J1.5 to 3.3 quite easy and instructions were easy to follow. I have yet to encounter a donation-requested-not-mandated (free) app of this high quality and was highly impressed by the developers commitment to excellence. Frankly, I was also very moved by the (your) generous sharing of hard work, without expectation of anything in return, given the few if any freely shared Joomla migration apps made available.
With that said, J2XML doesn't do everything for you, nor does it claim to.
For our NGO, the migration process has stalled for lack of expertise in customizing Jv.3 templates to match our Jv1.5. So, depending on your needs, your level of expertise and/or free time, you may find yourself in the same boat. It may be that there's an app out there that can do it, for a fee, but I'm under the impression the paid apps do not substantially differ in function from J2XML.
While an app capable of seeing the remainder of the process would have been ideal, the limited scope of the app in no way diminishes the quality of this developers' work. We've made it 3/4 of the way there, which means less funds going to a professional to get our site live again... So, THANK YOU for your help and THANK YOU on behalf of our community - families and the children who've been abused in residential and rehabilitation centers. :)