I've been compiling from source, using several different versions, now 3247, and wanted to note some operations that seem to be taking longer than they could. Disregard if the issues are known.
1) Viewing large files in .resx files. I just hit this one when I put Unihan.txt (from http://www.unicode.org/Public/UNIDATA/) in a resx file. It's 6 MB and the program appears to be loading and processing the entire thing when it's clicked. Maybe a size cap would be appropriate?
2) Manipulating Files in the Projects Tab: Especially deleting and moving. It may just be when SVN version control is used, but some can cause 30-second pauses for no apparent reason. Some project-local actions (delete a file, move it to a different folder) can force a recompile of the entire solution.
3) Adding Existing Folders: More a feature request, and maybe only an issue under version control. Right now, there's no easy way to add an existing folder. You have to move it to a new area, add the folder, then add all the files (and with SVN metadata in folders, it gets ugly). This is time-consuming when creating a project from an existing incompatible project format. If a folder was previously deleted since the last check-in, it sometimes won't let you create a replacement folder. SVN support itself seems to have a few issues right now, but I figure you're already working on that one.
4) Opening files at startup. Not a huge issue, but if you have a number of windows open when you close your project, it can be pretty slow to reopen the project. Maybe restricting the saved windows to those immediately visable would be a good idea.
These aren't large issues, but would make #D a bit easier to use. Thanks for all the work that's gone into it already. There's nothing else with such good Boo support.