Lately I found my self playing a lot with the Google search API, I would like to give my criticism about this one:

Cons:

• Old API as we used to in C (WinAPI) with 8 and even 10 parameters, no overloading.
• Only 10 results for each query, and they rudely ask for the maximum results wanted?!
  why isn't there any Const with maximum results so people could be aware of this 
  shortcoming.
• There is no ability to get the page rank.
• In their snippet result (where you can see intro of the text that found for this page) you
  will find it in HTML format, which I recognize as poor programming, there are thousands of 
  people who would like to see the results in WinForms, save into file or just read the text, why 
  should I make the formatting job (Isn't it all presentation stuff?)
• Least but not last, documentation for the methods (can be found online only.)

Pros:

• This is a productive tool for all the programmers out there, which can be easily download, install and use this fairly easy.
• Written as WebService which help for compatibility.
  

conclusion:

• As a programmer who need to search the web, I recommend this tool.
• As a programmer who wrote this tool I would run fast as I could and fix those Cons, and there is even more from the place they came from.

The Cons talk on their own, Does Google made this API poorly to prevent us from using it, or maybe they not as good as they seem to be.

remarks:
I hope they won't throw me out from their Ranking Servers :).
you can found more data in this article:
http://www.mattcutts.com/blog/feedback-products/