I have two IO ruched dresses, both bought to wear when I go out dancing the tango. They are lovely dresses, but have a high lycra content and are very tight. You can arrange them to be longer or shorter and they do stay where you put them. The ruching hides any underwear lines but your body outline is pretty much out there for all to see.
I love IO jersey dresses - I'm 5ft 9 ins, pear shaped size 12/14. I have the ruched dress in charcoal and the draped dress in silver and they are fab. I like the look of the zip dress - but in the slate rather than the bright Khaki pictured. With opaque tights it will look fine, you could always add a long cardigan if you wanted to tone down the "sexy".
I am trying to save for a leather jacket - even with the 15% off at the moment I can't quite justify it (FASHION15 if you don't have the catalogue - gets you free delivery too)