I tend to not think too highly of technical exercises. In my opinion, it is best to gain technical skill through playing things with actual musical quality, such as the Scarlatti and Bach mentioned above. (It will keep your interest much better that way as well!)
They are supperb to develop... tendinitis.
This is widely believed and simply not true. I tried it for years, isolating technical issues in the repertoire, repeating ad nauseam in all keys and rhythms, and it yielded little -- except boredom and distaste for the repertoire. Pischna, the Sixty Progressive Exercises, are designed to give you finger strength and independence. No musical considerations whatsoever. Just a workout for each finger. You perform them "lento' and "forte" with relaxed wrist and heavy finger strikes from fingers raised high to offer complete stretching of muscles and, therefore, complete strengthening. With the standard repertoire, your "exercising" efforts are constantly subverted by the musical dictates of the phrasing, etc. You have to divorce yourself from musical considerations to gain strength and Pischna offers just that: no music, no other issues but exercises. Thirty minutes a day and I promise you in one month you'll see amazing progress.Please don't debate me. Just try it and you'll see.
People don't play Hanon at concerts.
True, but too many people play concerts like they're playing Hanon.