I had a few transactions lately that took over an hour to get confirmations.
What is your experience with the expected delay of transactions without a TX fee?
If it appears as a "low priority" transaction and the queue is big, it could take hours, or days even. Thought at this moment, there are under 100 low priority transactions queued up: http://bitcoincharts.com/bitcoin/
So an hour to two is a reasonable guesstimate.
Is the minimum TX fee 0.01? (which is almost 20 cents, a huge amount!)
When that feature was being added for v0.3.21 the BTC/USD was near or before parity, if I remember correctly. Thus at the time that 0.01 BTC amount represented $0.01 USD.
Once v0.3.23 is released, you will be able to set a fee lower than 0.01 BTC, ... as low as 0.0005 BTC.
I would suspect that even 0.0005 will cause it to be included nearly always in the next available block, at least while the mining reward is 50 BTC yet.