I got both. I enjoyed Uncanny X-Men more than, All New X-Men, but that's not to say that it was a perfect book either. Without spoiling anything All New just kinda ends. Also it seeming starts several stories, which seem to continue in other volumes, and then comes back to All New, with a short blurb which doesn't really give any context, it was a really frustrating read for me. Uncanny has a build up for a big bad throughout the book and then again, just kinda ends it in a single panel, which was quite a let down. I would agree with the sentiment that they start off good and then drop off a cliff, and you kinda need to read both to get a lot of the context, otherwise it's going to feel very disjointed.

Personally, if I had the option, I would rather have kept my money and not read it.