Some time ago I've found a bug that I consider critical as it causes code loss.
I've already submitted a bug report but it seems to be not yet investigated by PyCharm team: http://youtrack.jetbrains.net/issue/PY-2992 so I'd like to ask here about it, maybe there are other people experiencing this issue and can 'star' it to be resolved quickly.
Short description is that PyCharm doesn't properly sychnronize files with filesystem while files are being opened. This seems to be a problem only if files are under version control (eg. Subversion) .
So, if you have file X.py in SVN repository and you update X.py file with 'svn up' (so that new revision is uploaded into your sandbox), then, if you open that just updated file in PyCharm, it will be outdated (version before svn up!). If you don't notice that it's not most recent file version and you start editing that file then you'll lose all changes that were taken from svn.
I consider it critical bug as you can lose your code and don't even notice that. What a mess...
I've recorded a movie that illustrates the problem. You can see it at:
http://natcam.pl/pycharm_sync_problem.mpeg (10 MB)
In short (movie description):
1. I have locally two sandboxes: pycharm_test/ and pycharm_test_copy/ that both point to same repository
2. Pycharm project is pointed at pycharm_test/ sandbox
3. I change file in pycharm_test_copy/ (sandbox that is external to Pycharm) and commit it
4. I issue svn up in pycharm_test/ (sandbox used by Pycharm)
5. File opened in Pycharm doesn't contain changes received from SVN
6. Few next steps illustrate that when file is already opened in Pycharm then everything works.
7. Next steps show that I can reproduce this problem again and also this may cause to lose some code (!) if opened file is immediately changed.