I am a casual user of Brightkite.  I use it to log into four or five different locations on a regular basis.  And I use it to do a couple of location-specific tasks – such as location posts and location photos.  But as a general rule, I use it only a handful of times each day.
But there are a couple of things I love about it:

• Entering location data is easy.  I have a few dozen Placemarks set.  And I can enter my location by referencing one of my preset Placemarks.
• Phone integration is quite mature. SMS data entry is a snap.  I can send an SMS message to a single phone number (after associating my phone with my Brightkite account).  Checking in is easy. And sending pictures and text are a breeze.

But I am not altogether thrilled with everything that Brightkite does.  Indeed, I have a couple of problems with it.  

• I have to build a completely separate friend/follower base.  I hate this.  I want to have one friend/follower/contact base for all my social apps.  It’s not hard to use Brightkite’s functionality.  But it is yet another user database.
• I have to use a separate user/password to signon to the service.  I really want a single signon or federated signon.
• I really want my location solution to integrate with my mapping solution.  In this way, I can do dirctions and distance calculations simply.
• I would love for my social systems and my location systems to work together.  Specifcally, I want to be able to IM or send tweets to folks that are around me.  And I’d love to have the ability to use XMPP as the infrastructure for these communications.  In that way, I can leverage the immense automation potential of Jabber-based systems.

Do I need another location-based system?  Probably not.  Do I want another location system?  M0st definitely.
Enter Google Latitude.
 This morning, Google told the world that Latitude was available for testing and use.  So I downloaded itand gave it a try.  Google Latitude does some things extremely well.

• Google gets the basics right. I can check-in. And I love the fact that I can use Google Maps to put a pin where I am located.
• Google does get the GPS fundamentals right.
• Google has mobile clients for all the major phone platforms (although I am hearing that the iPhone client really needs a little help).
• Google uses the single signon system that my other Google apps use.  More importantly, it can leverage OpenID in a federated model.
• Google integrates with Google Talk.  Hence, it is XMPP-enabled.
• Google integrates with Google Maps and Google Earth.

While it would be fair to say that Google has the framework and fundamentals right, it still needs to polish some of the rough spots.  In particular, the check-in process is particularly clunky – especially for phones w/o GPS.  Since GPS is avaialble on all “new” phones, Latitude reaches the tech savvy folks who like new toys.  But the reach is limited for those phones w/o GPS.  And the SMS functionality appears very immature.  There is no simple way to check in (via a service like Placemarks).  
Bottom Line: Google Latitude is a great first step.  It gets the fundamentals and infrastructure right.  But it really needs some work on the UI.  With a few more polishes to the UI, this WILL replace my Brightkite use.  But for now, I will use both and incur the overhead of doing the same thing twice.  This offering will force Brightkite to up its game or risk losing everything it has worked so hard to earn.
 
-Roo
P.S. Louis Gray has a great write up on Latitude and its impact upon Brightkite and Loopt.  His thoughs are available on his site.