Exporting OS X Mail from Mountain Lion to Snow Leopard

Question

After upgrading to Mountain Lion, I partitioned my iMac HD to have two partitions: Macintosh HD has Mountain Lion; I reinstalled Snow Leopard on Macintosh HD 2. Best part: you can access your user-created files from EITHER disk partition. But not so OS X Mail. I wanted to revert to Snow Leopard, since I don't like the iOS-like Mountain Lion (swipe THIS!), but Mail was a problem since all my Snow Leopard Mail was successfully migrated over to Mountain Lion during upgrade. But I think I found a way to Export Mail from ML to (a clean install of) SL.
Try this:
1.  Open Mail in ML. For each folder you wish to have back in SL, Export it to your ML Desktop as an .mbox file. Depending on the folder size, this can take from a few seconds to several minutes. You'll see an .mbox icon for the particular folder on your Desktop. If the word "partial" appears between the folder name and the .mbox suffix, wait a few moments for the Export to complete, at which time the word "partial" will disappear. E.g., for a folder named "Mary", if it's a huge one, the icon will first appear as "Mary.partial.mbox"; when the Export is done, you'll see "Mary.mbox".
2.  When you've Exported all your desired folders as above, you can exit ML and re-start your Mac in SL. Open Mail in Snow Leopard, and once again, for each file you just Exported in ML to the Desktop there, select "Import Data From Apple Mail" and choose the folder from the Desktop in ML to which your mboxes were Exported. When the Import starts, you can see via a progress bar how far along it is. When done, you'll see a new folder in your SL Mail called "Import"; click on it to reveal the folder you just Imported!
3.  Then drag the folder you just Imported out of the Import folder to "On My Mac" in SL Mail; you can then delete the Import folder.
4.  Repeat until all your folders are where you want them (in SL).
5.  When you have time, go back into ML and clear all those .mbox files from your Desktop.
There MAY be an easier way, but this is what worked for me.

Answer 1

The iOS view vs classic view in Mail is not the problem; I've already configured for classic view.
Mountain Lion itself is.
My short list (to date) of crappy Mountain Lion behavior; items marked with a double asterisk (**)represent the worst of Mountain Lion for me.
** No up/down arrows in scroll bar slider;
Expose` not as easy to navigate as in Snow Leopard;
Mail does not request passwords for either receive or send;
No "Save Draft" icon in Mail compose window (workaround: use command-s);
"Save As" selection missing in most app menus;
No separate Search window in Safari (workaround: use Firefox or Opera);
** Can't export Mail from Mountain Lion into Snow Leopard if downgrading (I compiled this list before I stumbled on the method in this thread, but I'd prefer to effect this with Unix symbolic links);
iWork 09 seems to have "circled the wagons" re compatibility with MS Office or LibreOffice (workaround: just use Libreoffice);