Here's a few things I'd like to point out:
1. Media in the preview window plays but it still continues playing (or actually it restarts) when the actual file is run. This causes the song/video to be played twice, creating an interesting but altogether not very useful "echo" effect

2. The Find Files feature doesn't work for me!
http://forum.zabkat.com/viewtopic.php?t=1664
3.1. Closing all the windows of xplorer2 does not end the process. Though this might be thought of as a feature, allowing faster startup, it does hog 10MB of memory for something that's closed, which I think is highly unnecessary. Though it is true the process ends if Alt+X is pressed, this is counter-intuitive, as I doubt a user would remember to press Alt+X instead of just the X button. IE, Mozilla and Explorer (if not running as shell) all take up a single process for multiple windows spawned from that process but the process ends automatically if all windows are closed. I suggest a similar take from xplorer2 or at least an option that would allow this.
3.2. Due to the above, the current implementation also loses user settings when the process is ended, even if by shutdown/logoff it seems. What this would mean is that, for example, if the user adds bookmarks in a session, closes all open xplorer2 windows and shuts down his computer, by the next time xplorer2 is started, none of the bookmarks/settings are saved. He would have to open up a new window of xplorer2 and press Alt+X prior to shutdown just to save his settings.
4. Related to 3, xplorer2 seems to favour a multiple-window config as opposed to 2xExplorer which by design favours single window operation though the user may wish to open multiple instances if it is his preference. This might be seen as a feature, but many features of xplorer2 enforce this style of usage (eg. opening a layout opens a new window instead of changing the current window's layout). For a user such as I, the two-pane-ness of xplorer2 is sufficient for everyday tasks and having to task switch between xplorer2 windows only proves to be counter-intuitive (just like IE windows). It would be great to have the option of single-window usage instead of being forced to use multiple windows.
5. More of a feature that can be kept in mind than a bug: the address bar currently holds a history. Wouldn't it be more efficient for the bar to have an auto-filename/directory completion as well as history (like explorer or the Run dialogue)? I remember having this discussion over 2xExplorer, but nothing seemed to come of it.
6. Another feature thing: bars. I don't know if this is different/reserved for the pro version but 2xExplorer had many bars like drive, sort and view bars. Here in xplorer2, all these seem to have been grouped into single buttons. I agree this does clean up the interface quite a bit but I think accessibility to these functions have decreased (design wise) since it requires an extra click and an extra target to find, as well as being unable to see which state the current view/sort is in as supposed to 2xExplorer where a single glance at which buttons are depressed will tell you what the current state is.
Other than that, great work! It's good to see xplorer2 moving on from the undeveloped, untouched alpha state it was in a while back.
Regards,
eXpiation