A SEO consultant has to be aware about his competition at any point of time. Which of them are ranking well. Not only just that but also how much traffic they are cornering, the movement on Google search rankings and ongoing SEO activities by your competitors.
For an idea on how to evaluate how to get rough figures of CTR of your competition check out http://www.seomoz.org/blog/defining-your-true-competitors.
It has summed up easy to use techniques. Results will not be very accurate or revealing but can be an important tool to measure your competition. Though, many SEOs like me rely more on checking competitors across a range of keywords and then ranking competitors accordingly. Why? because accurate CTR stats are hard to get by and may fail to give a clear picture.
Do chime in with your opinions.