I've used all types of 5x5's in the past... 5x5 sets across, work up in 5's to one heavy set of 5, two work up and 3 sets across of 5, etc. Its important to remember that for the most part, "5x5" is just a number of sets and reps. It is only as good as the effort you put into it and how you react to constantly changing factors; some of which are natural slows in progression, stalls, bad days, etc.
Of all of the variations and programs of "5x5" I enjoyed the Texas Method the most. Ran it for about 25 weeks and progress was equally split between weekly and every other week. Sometimes I was on a roll and had no issues increase weight while other times I had to hold back to allow my body to adjust to increases in volume. Sometimes I could get away with increasing weight on all 3 training session, other times I'd have to cut back on two of them to increase on the third. 5x5, or rather sets of 5 works well with the Texas Method for a while, but 5x5 does not define the program. Its actually less a program and more of a system... a frame work. Throw in what ever rep/set ranges you want that fits the idea volume work and do that until it stops working, from there, move to triples, doubles, or singles... less conventional but 4's and 6 reps can also work.
But past that... it is a good program that when fully understood, can take a lifter a very long way. Odds are that boredum will lead to major changes in programming before progress is dried out.