Is there something in your list that's broken when using TipTac? I have no complaints about it with WoD so far. I personally anchor the tooltip to my mouse cursor with a bit of offset, but I just checked to see if I could anchor the tooltip in the upper left and I could, however it still anchors the tooltip to the mouse cursor when mousing over items in your bag (which sounds like what you want anyway).
If you're still looking for a replacement, there's an entire section of add-ons dedicated to just tooltips -
http://www.wowinterface.com/downloads/index.php?cid=98
EDIT: Sorry, you said top center, but it doesn't matter since the tooltip can be anchored to wherever you want to drag the anchor to.