Most if not all modern dvd players now support both +/- and RAM disks. I burn with a Sony 4x +/- r/rw drive and have not had any problems with + media incompatabilities with my 2 dvd players and several computers. The problem occured as the format wars started just after the dvd-reading technology became mainstream. Thus the old/original dvd players would not read the newer formats. The - tech came out first and was based on the original frequency specs for burning media, but + writes at a different frequency and the older lasers couldn't interpret the binary bits. If you have purchased a dvd player in the last 1 to 2 years, there shouldn't be any problems.
Of course the most important factor now is the quality of the burning media. No matter what format you use only use high grade (ie brand name dvd disks). They cost more, but worth it with fewer coasters and unreadable disks. TDK, Memorex, Sony, etc. I have used them all and prefer either TDK or Memorex.
As for formats, - burns disks in a way that older dvd players had a better chance of reading, but burns slower (about 5-10 minutes depending on speed of burner - finishing [closing] the disk takes a while).
+ format burns faster (only a little though) and old dvd players didn't like the high density of the data rings. Newer dvd players (at most 2 years old) support burned media shouldn't have any problems.