Websphere Application Server

Hi,
Can anyone either tell me or point me in a direction to find out why we should be using "Websphere Application Server" (on AIX, if that matters), other than to put some money in IBM's pocket? What's the competition? In a (very) small shop environment that is writing the software that our < 100 employees business uses, is this worth spending money and time on? It is being heavily promoted to us and I would like to hear some non-IBM opinions.

Thanks for any suggestions or direction you care to offer.