Is there a chart somewhere showing the time it takes to get the 1st confirmation as a function of transaction fee % or transaction amount?
What is the average BTC transaction time and what other factors influence it significantly?
This page describes the criteria used in the reference implementation for adding transactions to the next block. Some miners use other criteria. In general, paying "extra" rarely improves your chances.
https://en.bitcoin.it/wiki/Transaction_feesI use the default settings to send, so when I have a lot of small inputs, I often get "Within 6 blocks/Medium Priority" rather than "Next block/High Priority". I'd say 90-95% of the time in my (anecdotal) experience, I get confirmed on the next block. Occasionally, though, I have to wait one more.