(Biologist, University of Minnesota; blogger, Pharyngula)
"...is Venter's technological tour de force a threat to humanity, another atom bomb in the hands of children?
"...to worry over a development that is far less immediately dangerous than, say, site-directed mutagenesis, is to have misplaced priorities and to be basically recoiling from the progress of science."http://www.edge.org/documents/archive/edge319.html
That's a pretty accurate summary. The only real difference between synthetic life and "real" life is that the DNA for synthetic life is custom-made in the lab. In many cases you could get the exact same DNA (and thus exact same organism) by removing and adding genes to an existing cell.
The real cool part about synthetic life is in the not-so-distant future you may be able to acquire a "base model" synthetic organism has only those genes needed for its replication. To that "base model" you would then add the genes you need to produce whatever products it is you desire. If designed properly, that base model could be built such that survival outside of a fermenter is impossible, thus eliminating the dangers of accidental release.
The later would actually be quite simple to do - don't give the cells the ability to synthesize amino acids, nor produce usable amino acids from proteins acquired from their growth media. Thus, the base models could only grow in media containing all 22 standard amino acids in a free form.