I did it - I've finally decided to change back to my maiden name. It feels very weird, but I know it's the right thing to do.
No one other than close family and friends knew about the separation (I personally didn't want to say anything to our wider circle until the divorce goes through as we're going for the two years separation ("no fault" bitter laughter) ground). As STBXH and I are still living together (financial reasons), people just wouldn't think to ask unless I mention it.
However, over a year after we separated, I'm still getting (from those that know about it) "Oh, I didn't think you were serious about it", "Honestly, why don't you just get back together already?!", "You're actually going to go through with it?!", "You're making a big mistake!", etc etc.
This, despite knowing that he:
(pre-discovery)
- cheated on me and carried on doing so until I found out
- lied to me about it for months even when I (suspicious) asked him to his face more than once
- told me I was cruel and uncaring about him and our DS when I suggested a trial separation to work through things
- played along in our "love-fest" post Christmas-2010 when we took some days to ourselves to get things back on track
- had already arranged and followed through with a threesome the day after we agreed to work on our sex life
(post-discovery)
- deleted all texts and emails so I couldn't get my hands on them because he was (supposedly) ashamed about what he had done
- admitted that he would have kept lying to me had i not found out
- stealthily read my threads for support on here because he just couldn't bear to "not know what I was thinking" (never mind me just going through what may have been more than half a year completely clueless about what a bastard he was being)
- told me it was my fault/choice we were splitting up
etc etc.
And STBXH - yes, you - I don't know if you still read any of my posts on here but, if you do, please know that I really do still hate you and though I dread the day where we have to sit our young DS down and explain that his family is not as it seems when either you or me move out, I shall breathe a sigh of relief when I no longer have to come across your hairs on my clothes/towels, your piss-stains on/around/under the toilet, your wank stains on your bedding, the sight of your godawful cringe-worthy (but yet so satisfyingly revolting) post-separation goatee, your ever-receding hairline and the fact that everyday I have to look at and be in contact with a person who may have to resort to finding another 16 year old to fall in love with them as they are the only ones impressive enough to fall for your non-existent charms and not see what an utterly damaged (and damaging) individual you can be.
However, as shit a husband you were in the last year of our marriage, I'll grudgingly admit that you are a good father (other than the whole "being happy to screw over and break the heart of the mother of your child" part). Please note that I keep the majority of the above to myself for our son's sake as it is not fair to poison the environment in which he resides any more than it already has been by your actions, and I am venting on here so that the "peace" remains at home. However, if you would like to know what I am thinking, do feel free to ask me 
Yes, I know, a lot of unresolved anger there which lovely DS hasn't noticed - I would like to say it's because I'm so good at keeping it under wraps (which I am - those in my family found out moths after we separated and were shocked as they had no clue!), but I think it's more because I work such long hours and see so little of DS that when I do, I never want my time with him to be sullied by how I feel about his father. We both still take him out on weekends, play together with him at home, but once he's asleep, STBXH and I mostly just ignore each other. DS does know that his father has his room and his mummy has hers, but that's about as far as it goes for now (he's still a toddler, so I expect the questions to start in the next 2-3 years, though I sincerely hope we won't be living together by then!!).
Aaanyway .... I decided today that enough was enough and my name change is just one more step of many to come.
I'm expecting a flurry of emails once people notice (and trust me, the culture/background I'm from means that they will, as much as I hope they don't for a long long while!). How to go about explaining? I don't want to go into the gory details but a curt answer like "I'm separated, it just didn't work out, we're living together for financial reasons, and I've got nothing more to say about it" will may come across to family/friends as a tad rude, given that STBXH and I were together for over a decade.
Don't really know why I'm posting about this (compared to so many other dilemmas on this board, this seems rather trivial) - I guess some hand-holding/support through this "momentous" decision would be appreciated