I have been a big fan of location/GPS based apps since I got my iPhone a few months back and I strongly believe the next big trend will involve location whether it's through Twitter, Facebook, or a third party - location brings the internet and social media to the next dimension. It also brings more advertising options so we can expect the big players to want a piece of this action. (ala Google, Bing, Facebook, Twitter, etc.)
Two mobile players I'll compare today are Foursquare and Gowalla.
Foursquare marks your stops by "checking-in" at venues and getting points and badges along the way. If you have the most check ins at a location, you are the mayor. The service works by simply firing it up on your iPhone and pressing "Check-in here". When you do, it can ping Twitter or Facebook with your location and a map plus any notes or tips you have added. When another user is already checked in at that location - Foursquare knows this and tells you so like that or like this.
Here are the negatives with Foursquare as I see them in Lehigh Valley:
I do not live in a "Foursquare city". I am always getting messages saying "we'll just pretend you are in Philly." Um, let's not pretend, we're in Philly because we're in the Lehigh Valley, mkay? This feature actually succeeds to alienate new users. This has already turned off new/ potential users and they've "checked out" on Foursquare. Yes, I'm talkin' to you @Mike0616, and you @poppet77.
The second issue is that there are hardly any venues existing in FS when I check in. I get that the new restaurant won't be there right away, but adding a venue in FS is a PITA because in order to do it properly, you need to get an exact address and 99% of the time, I have to look it up.
The last issue I have with FS, is the terrible job it does when I ask it to look up a location that I know is there. I tried to check in at a local mall that I know is on FS and it couldn't find it by GPS OR by searching "mall" near me. Come on!
Foursquare Score: 7/10
Gowalla has very similar features to Foursquare, except as @mandreano noted, it has a better interface. The design, colors, usability (@Usabilityarts - you with me?), icons, and layout are all superior to it's competitor.
Gowalla is used to "Check In" at a locations and can ping Twitter and Facebook (if you have geolocation turned on in Twitter settings it will include that in your tweet). When a location is not in Gowalla you can easily add it using GPS address (read: not typing out the address). When you create a location, you become the Creator and Founder of a Spot.
In the Nearby Spots section, you will see spots created by other GW users with a check mark next to those you've visited. You can visit the Nearby Spots or search by category where GW displays a map (that can be enlarged) of the location with your GPS displayed as well. Cool.
Other features include trips (ala tours) and a friend section to see what your buddy's are up to. For those of you without iPhones, you can use Gowalla at http://m.gowalla.com/
Gowalla Score 9/10
UPDATE 1/8/10, looks like Foursquare woke up and decided it would fix almost all the issues I didn't like. Oh boy - we got a fight on our hands!