All of them are 'supposed to', but that's just like the early days of single layer recordables. I have seen some compatability quotes of about 75%, but it was unclear to me how the disc's were authored and burned--which can have a huge impact on playback. Also the quality of the media (and about a thousand other things). Unfortunately the 'testing' is often anecdotal, or done by those who are very technically oriented, but often not very experienced with creating/authoring discs, mpeg file encoding, etc. I have done several projects using DL media, and have had them 'tested' on about 20 different players so far. I have not had a single problem to date, in fact, the DL discs play well on my 'testing' dvd player (a 1999 portable Panasonic which is very picky). I would however put my experience in the category of 'anecdotal', since I have by no means done wide spread testing. I author on DVDSP 3 and set the layer break there, output to an image file, bring the image file to my PC and use RecordNow to burn the image with a Pioneer AO8 using Verbatim media. The Pioneer AO8 automatically does the bit setting you would want for + media to improve it's set top acceptance and RecordNow fills the two layers with padding data(a requirement for the discs to playback as expected).