I had mine done a couple of weeks ago after reading about it on MN. I was very dubious as I'd thrown money at this before and got two different answers. I decided that since I was changing my wardrobe anyway (lost a stone and everything looked meh) I would blow £99 on a style day. I had mine done in Huntingdon and it was a fabulous experience. It lasted pretty much all day as we were all so fired up and chatty.
The very best part was the fact that when the other two ladies were being 'done' I could actually see with my very own eyes that 'their' colours suited them. One of the ladies was a 'Spring' and until they put the colours under her chin I had no idea what she was. She came alive right in front of me!
It also made me realise where I had been going wrong. My first colour analysis - done when I was in my 20's put me as a bright winter. I didn't feel that good in bright colours though so took it with a pinch of salt. My second session - given as a gift so thought I'd better use it - was a muted Autumn. I spent years in browns and beige feeling rather bleugh but the muted tones suited my personality better and I still wore navy and black anyway. 
Fast-forward to my recent experience and I mentioned that I had been analysed before and my consultant asked me not to tell her which. This consultation was done in natural light with my hair covered (I have golden brown (dyed) hair with very dark eyes and pale olive skin) and I'm a sure-fire sultry Winter. In fact, when the lady put the really dark pine green next to my face I was shocked. My actual comment was 'oh wow, you can see into my soul!'
It really was a fantastic experience for me personally, the lady could see why I thought I was an autumn but I left in no doubt that I'm a sultry winter.
What has changed? I wear navy and black with confidence, I've added a sprinkle of bright pink tops to my wardrobe, a cobalt jumper and a charcoal cardigan which makes me feel a million dollars. I've also invested in brighter lipsticks which I'm struggling with a bit but that's because of my wallflower personality that I hid behing a brown autumn instead of a sultry Winter.
I'm getting there!
Hope that helps you decide either way :)