FWIW, when that report was written, few, if any, of these self-leveling systems were around. They were talking about leaving a tile spacer in there, and saying it could cause variations on grout color...well, duh, the grout would be almost non-existent if it was not removed.
I've read lots of user comments on the things. One guy said his wall tile came off the next day, but then he admitted when they did, he didn't use the minimum trowel notch, didn't back butter the large tiles, and only had 10-20% coverage...well, again, duh...RTFM! Most of the other people complaining weren't using the proper trowel, either, or backbuttering the tile, or picking one up occasionally to verify they had good coverage. As with anything, there's a right way, and a wrong way to use it...it's unreasonable to expect great results when it is used incorrectly.
For a DIY'er, with large tile, even if you do need to spend a bit more time cleaning up the grout lines after setting, you'll end up with a better result, faster. A pro, maybe, depends. Few DIY'ers set lots of tile, and these aids, used properly, do help. Enough so, that some pros use them all of the time on big tile, too. On big jobs, it's not uncommon to have a lower paid helper, so leaving the cleanup to him, if the pro can set faster, still ends up saving money because of the speed he can set the tile.