First of all, this is nothing like reviewing proposals for, say, the NSF, where you have 15-20 page proposals and project sizes ranging from 3-5 years and anywhere from one to ten PIs. The Google proposals are (thankfully) short -- only 3 pages -- and generally ask for funding for a couple of grad students for a year, plus some funding for a summer month of a PI and maybe some equipment. So the individual grants are small, which in some sense is frustrating since it's hard to propose anything big and groundbreaking when it's just for a year. Essentially this means that most PIs are only asking for money for things they are already working on, rather than spearheading work in a new direction. (Arguably Google should be giving away more money to fewer schools for longer periods of time, but this is my personal opinion.) Also, NSF proposals are reviewed by a panel of (mostly) academics drawn from all over the place, who are supposed to be impartial. At Google, the reviewers are both researchers and software engineers who may or may not be working in areas related to the proposal itself.
Most of the proposals I saw left something to be desired. Far too many of them were asking for money for things that we already know how to do (like write an Android app for your pet project) or which have been done to death (like develop yet another mobile ad hoc routing protocol). On the other hand there were the rare proposals that had an exciting new idea and proposed to do something that Google was not about to go do on its own.
A few tips if you ever apply to this program (and I certainly encourage you to do so).
First, think about who the reviewers are. They are mostly not people like me. Most of the engineers at Google don't have a lot of experience reading and reviewing research proposals (let alone writing them), and many of them are not going to be in your immediate research area. Try to reach out and explain why your work is important at a broader level; the reviewers in this case are typically not your peers.
Second, think about why Google should fund this research. The key question I asked myself was not whether Google would benefit from the research, but rather why should Google fund a university to do this project, rather than just do it ourselves. If Google can hire a couple of engineers to solve a problem, I don't see any reason for us to fund a university to do it instead. On the other hand, if the university PIs are going to do something hard, or groundbreaking, or risky that Google would not have the time or resources to do, we should fund it.
There's also the related question of why should Google fund a research effort rather than another funding agency, such as the NSF. This one is a lot easier to answer: I know from experience that it's damned hard to get money from the NSF for many kinds of projects, and Google can help seed new research efforts that would be difficult to get off the ground otherwise. But if a project seems like it can and should be funded through another agency, that makes it less attractive from my perspective.
Third, try to get the exciting ideas up front. Most Googlers are extremely busy and probably won't spend as much time reading the proposals as you'd like them to. If you bury the lead it will be much harder for the reviewers to see the big idea and get excited about your work. It also helps to establish your credentials in the proposal itself -- not just your CV, but a paragraph or two in the main text saying who you are and why you are the right person to do this research is incredibly helpful (especially in the case when the reviewer is outside your area).
Finally, it always helps to have a champion at Google. If there is someone within the company that you know personally, who can vouch for your work and wants to work with you on a project, this helps tremendously. Having a grad student spend time at Google as an intern is a great way to make those connections.
It's just a guess, but I would not be surprised if other companies' research grants worked in much the same way. While I was at Harvard, I got a lot of funding through places like Microsoft Research, Intel, IBM, and Sun, all of which have fantastic university research programs. (Well, except for Sun, which no longer exists.) Of course, keep in mind that I don't speak for the rest of the Google Research Awards committee, and other reviewers very likely use different criteria than I do.
This is my personal blog. The views expressed here are mine alone and not those of my employer.