The other replies above are both correct. Read them carefully.
Before I began dual layer burning, I checked all of my standalone DVD players out over at the Videohelp.com website, and noted carefully what others had reported about their own experiences. (You may get lucky, and find that others have already posted whether a particular model handles DVD+R dual layer discs or not. I did, on three of my home players). I had to take a chance that they would play on the other units I owned, and I got lucky.
That said, I do have a friend who has three players, and they will not play at all on ANY of them. Just as some standalones do not like DVD-Rs, or some do not like DVD+Rs, or some do not like Video CDs, or MPEGs, etc., the same is true for the newer dual layer discs.
Mine even play on the DVD player in my wife's van -- now that is pure luck.
The "glitch" at the layer change may appear, but this is also true of commercial discs (in case you had not noticed). Some players handle a layer change better than others. And, the method you use to to actually bakcup your DVD (or authore or re-author your DVD) can have an impact on how well your player will handle the layer change -- if it handles it at all. Some users have reported that they tried re-authoring, and their standalone DVD player played the first half of the DVD fine, but choked at the layer break, completely, and could not go on. Because of these reports, and the high price of dual layer discs, I have so far decided to stick to exact copies of my original DVDs, with no re-authoring, using a disc image. I prefer using DVDDecrypter, and using it to do an "ISO READ" to the hard drive, and then an "ISO BURN" back to the dual layer disc. That way, the layer change is exactly where it was on the original commerical disc, and I end up with a virtual "perfect copy" of the original disc.