It's pretty important, and pretty useful, to do the unit turn and get the racquet up and prepared at the same time.
This way, if something stupid happens, like, a net cord hit, you can still run a bit forward with the racquet still up and prepared, then start the loop and swing.
The problem is, many people take the racquet back all the way, sometimes, too soon. It's better to start the racquet up immediately on the unit turn, then do the loop when the ball comes around. It's much easier to time, and you won't be rushed. In fact, you get more power from all that time to prepare.
Check this out:
http://www.youtube.com/watch?v=1ImeQaAyFPc&feature=related
From 0:00 - 0:07, you can easily hold that position for a while if you get a slower ball. Federer's rallying against an apparently faster ball, so obviously he doesn't need to hold up that position, and just quickly transfer from unit turn/racquet up to loop and swing.
You can see Kei actually hold this position a bit longer in this practice session:
http://www.youtube.com/watch?v=I5TXfkRS38Q
Notice how he puts up his hand and racquet, somewhat in a pause? That's what I'm talking about. Just remember to keep everything in motion; once you get your other hand and racquet up, you gotta keep it moving. You can, however, keep it moving slowly, exactly like how Kei does it.