Bitcoin is a non-sovreign currency with no central control. Operations are carried out on a distributed peer to peer basis. This latter is considered to be an advantage in that transactions have no oversight from governments and thier taxation and law enforcement systems.
Often used for the conducting of nefarious transactions but I have seen some semi legitimate online businesses offering to accept Bitcoins.
For businesses the two biggest issues that I see are those of security. There has been a lot of theft reported and when the FBI took down Silk Road recently they came into possession of a substantial proportion of all Bitcoins in existence. The second issue is that of volatility, the exchange rate against 'real world' currencies and gold cna change quickly and by large amounts which makes pricing in Bitcoins troublesome and holding them after sale can be risky for the issues of security and the volatility.
Related to IM?
No, not really, unless selling products and services that no other payment system will deal with - but if one is in that situation then one is not mainstream and would likely have access to alternate and less legitimate ways of getting money from punters' bank accounts into one's own.