Tim:
The 4th at the Black will be a pivotal hole in giving players the kind of momemtum they will need as they hit the stretch of holes #5 through #7 -- all good par-4's. That assumes no major misplays!
The fairway width will be the standard Open thing -- probably about 25 yards across. The key is hitting the tee shot as close as possible to the massive fairway bunkers that guard the left side. A slight draw can really set the player up to attempt a go at the green with the second shot. Given the elevated nature of the tee I'm sure most players will try to play a tee shot that is aggressive in order to score a birdie or possible eagle.
If you miss the fairway, either left or right, the type of lie you have will determine what club you can take to carry the cross-bunker. Keep in mind that rough has been extended on the far side of the cross bunker -- so just getting over the cross bunker will not automatically mean the player finds the fairway.
I can tell you honestly that if the player draws a tough lie off the tee the probability in carrying the cross bunker is indeed problematic. And, if you land in the cross bunker you will need Divine guidance to clear the high lip and THEN clear the frontal bunker and THEN hold the approach on the angled putting surface.
If the player opts to play short of the cross bunker after hitting the rough -- the 3rd shot will be from no less than 180 yards to a target that repels nothing less than an iron shot that drops softly out of the sky.
Players going for the green would be best served by playing their second wide to the right of the green in order to take the frontal bunker out of play. From that position the approach is far easier and the likelihood of birdie is enhanced greatly.
If you think you can reach the green in two you must hit a towering iron shot to handle the narrow putting surface. Go long and I as I said before you're deader than Elvis should the ball cascade down the far slope.
The 4th at the Black is supreme testament to Tillie's great imagination. I'm sure it will prove interesting to all players competing in the Open. In my mind, the Black only really begins at the 4th tee -- the first three holes are nothing more than just a warm-up to what comes ahead.