At the moment there is still far too little support from other developers, the comparatively time-consuming initial setup and error messages.
In addition only a handful of developers and without sizes like AndyB, AddonLabs, XFA, XT etc. the addon makes no sense to me. It's a shame - if something should change in the support from other developers, I'll be happy to correct my rating upwards, but currently only 3 stars are there.
Half a star less for using checkout codes to sell for free instead of offering straight away for free with no code nonsense.
I love it. It works perfectly and is light-years ahead of the XF 1.x equivalent. Adding support for multiple sources is an excellent bonus. I'll admit I had a few hiccups setting it up, but once I figured everything out the only complaint I have is a few possible errors you could handle better.
For example, right now, if you try to install an addon from an XF resource page, but the "download" button links to an off-site source, the plugin dumps a stack trace and just says "oops." It'd be nice to see a coherent error message instead of a stack trace, possibly with the stack trace in a collapsed div for those of us more advanced users who like fiddling with things!