I can't believe this had never occured to me before, but I am experimenting with collecting course survey results via Google Forms this year. So far, I like it!
Here is an example of the 8th-grade survey results coming in (but they have the rest of the week to finish them at home, since some of them were finishing up their projects today): http://bit.ly/Gr8CourseSurveyResults
Advantages: I can keep it for posterity without creating extra work for myself. I can easily share the results with my colleagues and my students. I can still view in each row what one individual's experience was like in my class.
Disadvantages: Still not completely anonymous. If I wanted to, I could trace who wrote the responses, based on submission timestamps and how quickly each student had finished their survey during class. If your connection isn't great or if the laptop isn't well charged, the kid could lose their work before/during submission.
But, overall, I think it's better than a paper survey! The kids are more likely to provide you with thoughtful answers, if they are typing rather than writing.
Addendum June 14, 2012: I decided to extend the use of Google Forms to grading our entrance placement exams! As an international school, we get a fair amount of applicants throughout the year, and today I was given 5 exams to grade on top of what I already am trying to finish up before the week is over. So, instead of just grading those exams, I decided to create Google Forms for all the questions and to enter in the ANSWER KEY as the first submission, so that future prospective students can be asked to submit their answers via the Google Form, to be compared by a math teacher quickly with the answer-key row in the same spreadsheet. This will make the grading process much easier, and we can still go back to skim through their paper exam if we need to drill down further into the process they took or to see how far along they got in the solution before they made a mistake. It will trim the grading process for each of those entrance exams down to 5 minutes, and thereby ease the load on all the teachers and also improve the turnaround time for the admissions people. I think it could be a win-win.
The only drawback I see is that if we allow kids to do this, it means that they will have access to the web while taking the exam, so in order not to skew their results, I think the admissions people will need to either be present in the same room as the kid while they're entering their final answers (after having completed the exam on paper), or give them a strict time limit for the computer-entry part (again, assuming that they have already completed the exam on paper). Because it's not machine-graded, if they are inexperienced in entering the expressions, such as if they put x2 instead of x^2, it should not matter to the teacher who is looking quickly through their answers. I am excited about this potential for seriously streamlining this grading process!