Usefulness
Russians are not very keen on foreign languages. Those who are often speak extremely the language they studied, but most Russians only understand Russian. They know theirs is a hard language and do not expect you to speak it. This means that even modest efforts to communicate in Russian will be welcomed with enthusiasm and unlimited forgiveness for whatever mistakes you might make. This attitude applies to Russians in their country but also when they are travelling.
If you travel to Russia, I strongly encourage you learn as much Russian as you can. Even a small number of words will prove extremely useful unless you wish to be remain in your hotel or gesture like a pantomine whenever you want something.
Doing business in Russia or with Russians abroad is greatly helped if you speak their language. You do not have to be Russian to benefit from increased trust and better contact through your knowledge of the language. Quite the opposite, Russians usually will trust more a foreigner than a fellow Russian! And if they can speak only Russian, they will rather deal with you than somebody else that they could address only through an interpreter.
Chic factor
Speaking Russian fluently is as chic as can be, especially in Western Europe. Russian has the reputation of being very hard (see below) and used to be a subversive language, spoken by revolutionaries and exiled noblemen. Many people in the West do not understand how Russia used to function, and have no clue how it works today. People who speak Russian tend to become clouded with an aura of shade and mystery. If you doubt that speaking Russian is chic, try yelling orders in your cellphone in a restaurant.
Travel
You can travel to a wide variety of countries on Russian, and get whatever type of landscape you want : desert, permafrost, sea resort, huge cities, etc... Russian is a very useful language to speak when visiting former soviet republics as very few people speak any Western languages. An added advantage is that very few tourists from outside the region care to visit Russia and its former empire. As a visitor, you really get the country for yourself. Locals are usually proud of the interest you show in their country and generally very friendly. This is in sharp contrast to heavily visited destinations such as France, New York, Venice or London, where even if you have doctorate degree in the local language as a tourist you will be still be treated as a lemon to be squeezed.
Culture
If you do not live or travel regularly to Russia nor have a Russian girlfriend, you need to make sure you can practice your Russian otherwise.
This is easy with Russian! There is a wealth& of books and DVDs waiting for you, and many are accessible from the internet or even at local Russian shops if you live close to a Russian expatriate destination.
The ressources available on the Internet in Russian are incredibly rich. You can find millions of high-quality newspaper article, commercial website, download Russian music, etc...
You can spend hours reading about local news, or strange faits divers that happened in remote places in Russia from your web browser.
And if you travel to Russia, you can buy truckloads of CD-ROMS, DVDs and books for pennies in the many open-air markets in large cities.