Another user interface concern from my side (please note that I am an industry expert in user interface and design).
I think the use of a progress bar to indicate how many coins have been anonymized is misleading to new users.
Progress bars are usually used to indicate the progress of a download, installation or file transfer. The main goal is to reach 100%. If progress bar does not reach 100%, the operation will be useless in all cases.
With darksend+ this is not the case; anonimizing 30% of your coins and then stopping could be a useful operation depending on the user's needs and intentions. It is not the main goal to reach 100%, or at least, not always.
I'm worried that the user will think he has to anonimize 100% of coins in order to have a successful operation, due to the use of a progress bar which I think is a misleading control in this case as it will be associated with common uses. It is arguably even a wrong use of this control, but I'm not sure of that. Percentage is a secondary type of information in this case, but it is presented as primary due to use of control.
To de-emphasize the anonimized coins in relation to total number of coins in wallet by making it a secondary piece of information, I suggest the following:
1) Instead of a progress bar, simply display percentage in text. Remove progress bar. Example format: "x of y coins are now anonymous (z%)" -- presenting the text like this will clarify the immediateness of the progress further in case of any remaining confusion.
2) To give the user the sense of a process being active, display an animated spinner or indeterminate progress bar while anonimization is active. An intermediate progress bar uses motion or some other indicator to show that progress is taking place, rather than using the size of the filled portion to show the total amount of progress.
Thoughts? I wouldn't say this is critical for RC5, unlike the addition of Start/Stop button, which was a massive win.
Diirk (coinzcoinzcoinz on BTCtalk)