Couldn't resist reviving this one.
I've been taking singing lessons since first reading this thread, and its amazing how my opinions have changed, and how much of Alice's advice (in this and other threads) is spot-on.
First of all - proper tuition and exercises make a huge difference to the voice. I used to sing low and loud all the time, but it turns out I'm soprano & haven't been using the best part of my voice at all.
When I first started the lessons I had a very powerful developed chest voice & just a really weedy head voice. Over the initial weeks the position of the breakpoints revealed that my natural range is soprano. I gradually built up a range of good quality high notes by exercises & these are now just starting to be accessible to me in songs (to start with they were only there in the exercises).
Up until very recently I was concentrating so hard on technique that the songs Tania was teaching me via were coming out very unemotional and dull. There was also a very definite gulf between what I was learning and what I was singing at pubs & sessions (which was lagging the lessons in quality but retained the emotional expression - I continued to sing in my old voice because the new one isn't ready yet...).
Over the last few weeks Tania has been concentrating on getting me to put some communication into the songs - which is coming along slowly. Steve t advises (above) that if the lessons take the expressiveness out of your voice then drop them - but I'd argue that its worth sitting it out a while because the expression will very likely come back in just as soon as the techniques become second nature (which they do, and then you'll have more tools to express with.....)
I'm really pleased that I'm taking lessons as there is no way I could have got this far on my own. The only downside is that the more you learn the more you realise how much there is left to learn. But its well worth it...
The techniques I have learnt have spread from the exercises to the taught songs and then into the folk & blues songs that I really love singing. Just because the teaching is done in one style of music doesn't mean that it doesn't apply to the style you want to sing in.
The thing I'm struggling with at the moment is that transition between chest & voice - and trying to get the two powerful ends of my voice to meet in the middle (big gap at the moment I'm afraid).
Reaction from friends is that the lessons have been worth while and have made huge improvements in my singing, one saying that I've gone from "someone that turns up and just does their best" to one of the better performers at the session. I even impressed my husband two weeks ago at a party - but then he had been drinking.......
Another thing in favour of vocal exercises....... I assume its to do with the muscles used, but after singing practice I feel exactly the same way as I do after a damned good seeing to! Sets you up for the day, it does!
So - if you're thinking of taking lessons - then my advice is to go for it.......

Cheers'm'dears
Kris