I use to be a bigtime adwords spender (see my google frig) but have reduced it to a much smaller spend in the last six months and done very little management of it. Face-to-face with the optimizers, this is what I learned.
1. I set up my campaign with the conversion tracking a mix of email sign-ups and customer registrations so the conversion data in the account is useless. I set up the sales count data accurately. But the adwords interface is setup so that to look at my conversion rate (the sales count variable) by keyword or campaign, I need to go to the report center and generate reports and analyse spreadsheets. Why can't I change the variables that the account shows in its default reports?
2. Effective analysis means being able to aggregate data across a number of different variables to get patterns and to find statistically meaningful data. A pool tool would allow you to do all the analysis that we now do using sorts and filters in spreadsheets. For more info, the pool tool.