Alice - I've had plenty of good feedback, and I can hear a huge difference myself too.
Friends that I sing with have commented that I have got much better, and that the improvement is still ongoing - but some of that can just be confidence.
I think where the lessons have made the most difference is in giving me a huge choice of different options in singing - so that I can put a lot more texture into the songs. That also allows me to vary the way I sing a song, so that keeps them interesting.
I always had compliments on my voice & singing when I sing in pubs, & still do - so I know the lessons haven't broken anything :>) . Though I do make some appalling errors of judgement sometimes.........
I minidisk my lessons so that I can practice in between, and I absolutely cringe when I hear the early ones. I also periodically minidisk myself singing & I can hear a big difference there too.
Since I've started to sing some operatic repertoire my next door neighbour claims to enjoy listening when she's on the loo or in the bath!!!!! I can't see my folkie friends appreciating the opera-stuff - but I know 100% for certain that the operatic style of training has improved my folk singing.
Even my husband reckons that I've got way better (and he's terrible hard to please). I just asked Hammerite what had improved since the lessons & she said "everything".
So - overall feedback is good, and there is a big noticeable difference between the before & after.
My teacher is not fond of folk (she thinks its all too miserable!!!) - and we often laugh about her corrupting my folkiness with her operatic stuff. However - last week she told me she was going to perform some "English Folk Songs" with a friend - these being classical arrangements of trad songs. So now I can claim to be corrupting her right back (sort of). Though she did emphasise that they are classical arrangements & her that voice is not folk and the violinist is not a fiddle player.

Kris