Sheesh! just use the command line client. It has none of this bullshit.
As mining becomes harder transations sent without transaction fees will be unlikely included in one of the next blocks. I think it is best to think of transaction fees as a bid offer towards the miners to include your transaction. It is up to you to pay a fee and up to them to confirm your transaction in a block. There in no fixed transaction fee and since finding a block is a random process (i.e. a mining pool will find blocks in a frequency based their share of the total computation power of the network) sometimes you might be included earlier .. sometimes later (depending on the policy of the mining pool that found the block). The higher your bid for inclusion in a block the more likely it is going to happen with the next block.
