.. a 'good' thing? Is it a step in the 'right' direction? Should we be meddling with Nature at this fundamental level? Where is 'the line' and not will it, but when will it be overstepped?

I'm not sure what line you're speaking about. Do you speak about an ethical line (with regard to embryonic stem cells) or more about a line in regard to "experiment out of the lab"?

There seems to be quite a potential in scr to find cures for chronic diseases.
But if for you genetical engineering is in the same vineyard as stem cell reasearch, I can see a bolt red line.

To be honest, I don't see that there is an "ethical" line in science. There are actions and there are consequences.

Some consequences are desirable while others are not.

A great example is stem cell research. There is not a very clear line. If you think any kind of abortion is horrible, then it's not likely that you will appreciate the consequences of using stem cell lines from fetuses. However, there is still the potential to cure some fairly awful diseases. Of course, this is only a debate until such time as stem cells can be harvested in other, equally useful, ways. Then there won't be a debate. Until next time the line is crossed.

There are quite frankly a number of types of research that worry me far more.

I am often appalled that the major powers continue research into bio-engineering lethal viruses to use as weapons. Viruses are dangerous enough as it is without adding to their lethality on purpose.

There is way too much merit in SCR for all sorts of things to consider just 'ignoring' its existence now. Unfortunately once something has been discovered, it cannot be undiscovered, and the discovery of stem cells and their potential will beat any 'line'.

SCR promises much. It might in future save millions, curing millions of conditions. Think about it; a cell type that can become ANY cell? Massive potential, which we should use.