There is hardly any disadvantage of this new technology. However, at this present, there is a temporary disadvantage, that is VCR is not yet available in a mass numbers. Maybe because it is still in its early childhood. But in a soon future, it will become popular to its customers with low cost, when it is distributed in mass numbers in market.

Another disadvantage of VCR is that if the subjects is predominantly retinal damaged, then there is a slightly disadvantage for using VCR

http://www.mudoc.com/hdmm.htm
http://www.ncbi.nlm.nih.gov/pubmed/11563496
http://eyeoverheard.files.wordpress.com/2009/03/virtual-retinal-display.jpg