I can honestly say that I've fallen into the trap of 'hourly rate' vs. 'results able to produce' too many times. The Guerrilla Marketing guys have an interesting take on this phenomenon, and call for the end of hourly rate quoting by consultants all together. Not to make a huge case out of this whole thing, but I think of this from the client perspective (as if I were the client) and try to put a monetary value on what it is that I'm seeking (knowledge, an improved system or process, whatever...). Helping your clients come up with a business case for their project can be an integral part of your pitch, thereby supporting your involvement and the value you bring.

There's another lesson at stake here. It comes down to the point of working smarter vs. working harder. You can put all the grunt effort into a project that you can muster, but it still may never be the most expedient and intelligent way to get the job done. Step back, think "results", and plan your work better accordingly.

I have been doing consulting foro over 8 years and I agree with doing away with the "hourly rate" issue. I have worked with a larger consulting company where it was difficult to meet all the projects needs when we were billing at $180 per hour with an average budget. I knew I had to get specific things done with the allocated hours and I had minimal time to perform other very pertinent client concerns.
I have since moved to an organization that performs fixed bid system implementations and it has been fantastic. We are happy because we do not feel rushed to get the system in and can take the time to make the client happy, and the client can rest assured they are not getting green apple consultants in their door to sit there and "learn on the job" while charging them.
Clients need to not only look at the rate/hour when looking at consulting, they need to ask themselves the following:

1) Even though the rate/hour goes down, I may get consultants that will take twice as long.
2) Is the consulting group motivated to complete the project successfully or will they drag it out to collect more "billable hours"
3) What assurances is your consulting company willing to give you that the project will truely take the time described?