Upgrade my Globe Vienna for commuting and distance riding, or look for a new bike?
You mentioned long distance ridding.  Here is what I would be thinking about: 

Comfort

When I think about comfort there are two things that I think about.  Most importantly I think about handlebars and more specifically how many places you have to put your hands.  Drop bars are nice because you get three positions, but I don't like drops when I am riding socially.  Check out the handle bar page to have a look at your options.  

Also thinking about your saddle will be pretty important.  

Point: probably it is possible to upgrade your bars and saddle to achieve a more comfortable ride

Speed


Put on some slick tires 
Weight of the bike is important (especially in hilly areas) 
How aerodynamic can you become on the bike? 


Cargo


Will you want to mount saddle bags?  
How many water bottles can your bike hold?  


Other


When I do longer rides I usually bring along a friend.  What will your friends be riding?  You don't want to have a bike that is too fast (or too slow).  
What kind of terrain are you going to be riding over?  Do you want to have slick tires (and narrow wheels) or wider tires?  Will you be riding in winter?  Most road bikes do not have enough room for studded tires.  
Are you going to leave you bike locked up outside (while you are at work, getting groceries, etc)?  You don't want to have to worry too much about your bike.