From your explanation I understand that the parameter is for filtering transactions that are relayed?
What I thought was that this parameter is to specify a minimum tx fee to include, even if the transaction is smaller than 1KB. Currently the rules implemented in the bitcoin-qt client sends some transactions without any fees if they meet a certain number of criteria. There is no way to enforce that a fee is always used?
that's a different setting. paytxfee is for how much fee per kb.
also, release notes for 0.8.2:
Fee Policy changes
The default fee for low-priority transactions is lowered from 0.0005 BTC
(for each 1,000 bytes in the transaction; an average transaction is
about 500 bytes) to 0.0001 BTC.
Payments (transaction outputs) of 0.543 times the minimum relay fee
(0.00005430 BTC) are now considered 'non-standard', because storing them
costs the network more than they are worth and spending them will usually
cost their owner more in transaction fees than they are worth.
Non-standard transactions are not relayed across the network, are not included
in blocks by most miners, and will not show up in your wallet until they are
included in a block.
The default fee policy can be overridden using the -mintxfee and -minrelaytxfee
command-line options, but note that we intend to replace the hard-coded fees
with code that automatically calculates and suggests appropriate fees in the
0.9 release and note that if you set a fee policy significantly different from
the rest of the network your transactions may never confirm.
