First I tried some of the technologies Google Labs have made public and found them to be amazing. I was very surprised to learn about goog411. Fantastic idea.
The experimental ones weren't as impressive, but hopefully they will improve with feedback and the lab team. My favorites are:
Google Suggest, because it saves time typing and helps if you aren't sure about the spelling, or phrasing of a subject. I expect this lab to be put into use.
Google Ride Finder is a cool idea, and would be very helpful to those that find themselves in need of transportation quickly in a strange city with the use of a cell phone and internet.
Google Page Creator would be a terrific asset for many who know little about this task, but want their own web page. I didn't want to make a page, but it appears to be very user friendly for those that do. If it works as they claim, I think it would be greatly used by the public.
Google Mars was amazing and fun to explore. I don't know how many people would actually use it, if it went public, but maybe more than you think.
Google Music Trends was interesting. Fortunately they had an explanation on how it works and how to use it. I spent a fair amount of time looking through this one, and thought it was good to find new groups in a genre, but I was disappointed in the small amount of groups they had under each genre. Perhaps since the list is created and updated by the Google Talk listeners, it limits the music added, and the genre it's added to. They didn't list Techno, and the Electronic and Dance genres didn't fill that gap. This might be used a lot in the future, because it's a quick way to reach information about groups and new music, but I feel it would have to be improved to be more inclusive.