I've owned 7 Kleins over the years: 3 Attitudes, 2 Pinnacles, 1 Rascal, 1 Palomino (current ride). The oldest of the bunch are 2 1990 Pinnacles, 1 1992 Attitude, 1 1992 Rascal. These were incredibly strong frames despite the ultra-light weight. I still own the oldest Pinnacle frame, The Mule (pictured below, and in my avatar), and am getting ready to build it up for yet another life. That frame has suffered mightily, including outlasting an Answer AccuTrax fork (cracked at the crown), crashing broadside into a car at 35mph and bending backwards a Spinner fork and bending a Deore XT axle, but not doing any damage whatsoever to the frame!!! I've had the bottom bracket bearings replaced twice, still have one of the oldest Chris King NoThreadSets in town, and have the original 1990 Deore XT seatpost I bought for it. I have no doubt whatsoever that the frame is still strong.
In a cross-over to the 'RIP for Long Lost Bike Shops' thread, I bought my first 3 Kleins at Valley Bicycles in Chatsworth, a shop that just recently closed and was replaced by a Cycle World spin-off from their Northridge store. The first Attitude I bought, the 1992, was purchased unpainted through the Chatsworth store, and I drove it to Curtlo Cycles on Sand Canyon in Santa Clarita for a custom paint job.
Though the most recent of my Kleins, a 2001 Attitude and a 2003 Palomino, are Trek builds and noticeably less stout than their ancestors, they are still wonderful machines.
The Mule, in a mid-life build:
