I know of friends who did controlled crying with their six month old - and it worked wonders, by the end of the week they were sleeping through the night, they certainly didn't seem to suffer for it.
I also know of (quite a few more, I must say) friend who have tried it and found it unsuccesful.
It has not worked with our two, although we did do something along the same lines with Molly to get her to sleep through the night when she was nearly 1 - I started settling her at night instead of DW, no more breastfeeds every two hours, but there was no letting her cry it out, I just went in as soon as she cried and settled her straight back down. It was tough for a week, but it worked.
With Olivia there was no way! :D She has been ultra-clingy since birth, and in hindsight our biggest mistake with her was that we didn't just think to put her in a sling and wear her earlier. She just wanted to be held so badly, but health problems and life issues in general were really putting the pressure on, so there were a few nights where she did cry it out because her parents were just emotionally exhausted.
I guess no one said parenting was meant to be easy.
Olivia is still clingy, but she is the most gorgeous adorable, loving little toddler you could ever hope for, and she adores her family and her sister.
I think sometimes you have to go with the flow and try these things. There's no shame in trying something new - and props to you for recognising that it wasn't going to work for you and moving on.

