I think it is a great way to add size and strength but I would suggest doing some lighter (higher reps) days. The 5x5 doesnt leave room for variety in volume, reps. I would just throw in higher rep days here and there quite often just to keep the muscle guessing and to make sure the all fibers are adequately stimulated.
I tried the 5X5 training style and it didn't work for me
but then again I was forced into only being allowed to do a training split that was divided into 3 days.
day 1: Incline, decline, and flat bench
day 2: power cleans and military press
day 3: Back Squats and dead lift
it didn't work out well for me my maxes all dropped most significantly in my bench press I lost 20 pounds and my size actually went down
day 1: forearms: wrist-curls 5x5, reverse wrist-curls 5x5, reverse arm-curls 5x5
day 2: triceps: over-head DB ext. 5x5, Push-downs 5x5, kick-backs 5x5
day 3: calves: calf-raise 5x5, seated calf-raise 5x5, donkey-raise 5x5
day 4: abs: crunch 5x5, pelvic-tilt 5x5, hanging knee-raise 5x5
day 5: traps: DB shrugs 5x5, BB shrugs 5x5, upright rows 5x5
day 6: delts: behind-neck press 5x5, front-raise 5x5, lateral raise 5x5, BO lateral raise 5x5
day 7: quads: leg-extension 1x5, leg-press 1x5, stretch 1x5
day 8: back: hyper-extensions 5x5, behind-neck pull-down 5x5, CG pull-down 5x5
day 9: obliques: DB side-bends 5x5, squats 1x5, broomstick twists 5x5
day 10: repeat
Oh, and change splits every 2 weeks to keep the muscles guessing! When muscle realizes that its confused, it WILL grow! FACT! Muscle gets easily confused by altering between high and low reps. Also doing curls on different preacher-benches will confuse your biceps totally! Muscle is naive! When doing 5x5 the muscles just go like: "WTF??? I'm totally confused so now I'll just GROW!!!???"