I personally quite like the tabs being on top. However I have one relatively big complaint about them...
That being that I can just click on a tab and instantly be taken to it as I could in Safari 3 and any other browser. Here I have to hover over a tab for a second and then click. If I click instantly, I end up dragging the whole window... Just a bit of a pain in the rear.
Hoping they'll polish that behavior by time final is outta the door.