I'm separated but not divorced. Divorce is not yet in process and probably won't be until we've been separated for two years or however long you have to wait.
I wanted to separate but it's been really hard, like you said Dahlen lots of reflection. I still feel a long way off wanting a new relationship.
You are probably right it is a process that varies from one person to the next so it is a risk that the other isn't in the same place as you are.
Personally I'd feel very wary about getting seriously involved with someone who was separated. Separation is easily reversible. The person could go back to their spouse and it would be very difficult if that happened. On the other hand, someone separated might be looking for something without too much commitment which could work well if you felt the same.
The religious/legal side of it - the fact that someone is, on paper, still married wouldn't be an issue for me.
I think also the circs make a difference, how far on from each other the former spouses are, how amicable they are, etc. Plus whether there are practical issues to consider like if a new relationship might impact on a divorce or settlement.
Sorry lots of ramblings there, been sitting in the sun this afternoon.