Here's my nickel BreadSkull; for me, since the very beginning I placed everything on one drive, OS-10/9, no problems. Before the big update I had a few funky quirks, but I expected some, after implementing the update all of those little qurks have literally gone away. I have so far helped 22 friends of mine,(who are also hardcore Apple folks) since the March update release, and so far all of these people are having much, much, fewer or no problems at all comparatively when they had their systems partitioned-out. And I have just finished surveying them all today, and all of these people are current, with 10.1.1, all but 1 is happy with OS-X now; and all, but this one, now seat in front of OS-X everyday. Oh, that one person who is not satisfied is someone who just does not like OS-X at all
, he simply hates the GUI, AND THAT IS ANOTHER ISSUE THAT SHOULD NOT BE STARTED UP HERE. So overall to your ?, I say nay to the partitioning the HD.