1. When i edit a file in MC and save, what quality settings are used? I know rotation is lossless, but how about editing? I saved a few files, and the file size seemed to increase. Oh and I am using JPEGS... not lossless.
rotation using the editor is
not lossless. rotation using the commands available from standard view
is lossless. any other editing is lossy by nature.
2. Is file metadata/tagging preserved? EXIF?
It depends on what you do, and how MC is setup.
If you perform a "save as.." in order to preserve the original file, a new file is created, and it has absolutely no metadata whatsoever. No file tags, and no database info. It will be a brand new file that will need to be tagged from scratch.
If you simply save the edits over the top of the original file, then you still end up with a brand new file with no metadata whatsoever, but you will still have any previous tagging info for that file in your MC database. You can use the update tags from library to re-write the tags. EXIF info is permanently lost. Also, in this scenario, if you have auto import watching the folder the image resides in, you need to get that tag update done before Otto wakes up (either be quick, or unwatch the foder) because Otto will see that, essentially new, file as having received external changes and promptly set about updating things!
3. Is anyone using Image Editor on a consistent basis as part of their photo workflow? Impressions?
If it could preserve all metadata, I'd use it. It's quick, handy, and it works well for those simple things like red eyes and cropping. As it is, I personally, don't use it.
Can I trust MC with my files? 
Yes. Though it's also the end-user's responsibility to understand what MC will do when he/she clicks a button here, or a tickbox there
-marko.
Thanks to some help I received from other interactors, I have a
batch file here that makes a copy of a selected file, then opens that copy in photoshop. You simply add the batch file to MC's external programs list. (Send to... (external) > add/edit programs.)
I make sure that
all my image related tags are saved inside the file, and that auto-import is watching my image folders.
While I'm working on the file in photoshop, Otto gets to work importing it. As it contains all the metadata of the original file, it shows up beside the original regardless of what filters are in place in the current view scheme.
When the file is saved in photoshop, any EXIF info is preserved, but the proprietry MC tags are lost. This is not a big deal however, as that info is, by now, safely inside the database and the update tags tool can rewrite the <MJMD> info.
