I'd be interested to hear from advertisers & agencies as to what keyword management technology they're using to manage their AdWords campaigns. Google has ~55-58% marketshare in the U.S. but it seems as though they're closer to 75-85% in the UK & most European countries.
As such I imagine that presents a problem for people using tools that were conceived for Overture's transparent bid environment.
Since Googles interface has recently added the time feature (adjusting bids by % of max bid during certain time slots), plut the fact bid gapping and other bidding strategies that make ppc management software attractive, cannot work on Google, (you don't know what the competition is bidding, therefore you can use the tool), I think the interface that they provide, along with analytics is your best option.
Sorry, I should've been clearer. The percentages I listed were of search marketshare.
The point I was making was along the lines of what Gary said; namely that I don't see how a system that requires knowledge from the search engine of what price gets what position can actually work on Google. Google's Traffic Estimator is broken, and you can't effectively use a rules-based bid mgmt system if it a)depends on knowing bid/price relationship; and b)uses Google's [broken] traffic estimation to figure out what volume each keyword can drive.
This is all the more of an issue in Europe because Google has such dominant marketshare there, which is why I'm asking the question. I suspect that either advertisers aren't aware of this [yet], or growth in keywords and traffic is making any SEM's management of a client's campaign look good right now. This was the case in the U.S. until mid to late 2004, at which point large PPC advertisers started to realize that their campaigns were plateauing once all the easy hits were had.