I like it, the shading is really good and I love how you did the face (its miles better than I can do from scratch at the moment). The upper part of the dress is really good but it looks a little like you over-smudged the skirt a bit. Next time you could try using a mixture of the paint and spraypaint tools with some changes in opacity and whether its darker, overlay - things like that a little more and tone down how much you use smudge/blend tools. Over all though it is better than I could do at the moment. Its really amazing that its using a mouse when you look at the body and top.
I know what you mean about how rare it is to get someone to post good constructive criticism. Heart breaking when you see so many pictures that have "critique requested" tags yet have been untouched by useful comments for months.
This is my 4th account (I've been slowly deleting my other accounts) but I had loads of art up between all of them and am going to build up my gallery here - and I would badger my family and friends to try and get them to join up so they could critique on pieces. Only some refused and some just were NOT constructive just giving me "better than I could do" comments (great for the ego, awful for improvement). But if I manage to show my mother some artwork offline she will critique except I have no printer so I can't exactly show her digital art offline and if I show her over net she has no interest.
It kills, I mean - I get why they have "feedback" groups on here... except I've submitted to a feedback group before and gotten sweet feliss in answer.