I've namechanged so as not to out myself in rl since I've been telling lots of people about this (but have been on mn since 2007, mostly lurking), but I got my colours done recently and it was amazing. Until I started reading the s&b boards earlier this year, I hadn't even heard of it (actually, thinking about it, I seem to be trying to live my life according to s&b, including using the oil cleansing method, coconut oil on my hair, and the wearing of scarves!). I've tended to stick to safe black in the past, but wanted to be bolder, but wasn't really sure what would suit me (and with two dc, time to wander round the shops isn't exactly in great supply).
I saw a House of Colour rep, who went through it all in a lot of detail. The best bit was sitting swathed in the scarves, and seeing the differences that a small change in shading can make to my complexion. Other posters had said that you can really see a difference, but until you see it yourself, you don't realise quite what it's like.
We started with the darker end of the spectrum, Autumn and Winter, as I have dark hair and dark eyes. The scarves were layered up in a mix of the seasons, e.g. a green from Autumn, and a green from Winter, a blue from Autumn, a blue from Winter, etc. As they were removed one at a time (not in a dance of the seven veils type way 
), you could really tell which scarves were from the correct season as they really lit up my face. It was kind of like 'okay, okay, wow!, okay, great, okay, wow!' as they were removed and a new one could be seen.
Of the thirty-odd colours in the season, there were about three which didn't look right on me, lots that looked good (including black, thankfully!), and about half-a-dozen which looked amazing (mostly bold, jewel-like colours, although also dark charcoal grey. I am a sultry winter; that may be the only aspect of my life that can be called sultry, but I like it!). It's given me a lot to think about, and I've done a quick bit of window shopping since. I found myself glancing round a shop quickly, and focusing in on areas with 'my' colours in, and ignoring the rest of the shop.
If it's something you're vaguely thinking about, I highly recommend it, and thank you mn, for telling me about it in the first place!