You mean the use of liposomes, yeah those have been ok in getting the DNA in. But in the end it's not just about getting the dna into the host cell, it's about getting into the genome so it can be passed onto the daughter cells. So far, it seems like the reverse transcriptase and integrases from retroviruses have been a terrible idea. People(chemists, biochemists) are more interested in creating their own catalysis machines, meaning it's no longer made out of protein. The subunits are not amino acids but novel nano compounds.