The K6 is very compatible to the current Socket 7. The 166 and 200 MHz versions are running at 2.9 V split voltage, which you can find on all new motherboards. The K6 233 is supposed to get 3.2 V, but it runs fine at 2.9 V as well. Only overclocking gets kinda difficult to impossible at 2.9 V. The solution to this problem is a trick with the voltage jumpers on all boards that have jumpers for single/dual voltage and other jumpers for the core voltage itself. Here you can adjust the jumpers to dual voltage and the core jumpers have to be adjusted to 3.3 V. This is 0.1 V too much, but that's ok in terms of heat and reliability and makes the CPU wonderfully overclockable. In fact this is actually the jumper setting the K6 system came with from AMD. Future boards will include the 3.2 V setting, like e.g. Shuttle boards or the Asus TX97, which falsely uses 3.1 V, but it's running the K6 at 262.5 MHz fine. The next generation of K6 CPU's will be manufactured in .25 micron technology and this will reduce the required voltage down to 2.8 or even less.
Software runs without any problems on the K6. I've tried several programs, and the operating systems you can see above. NT always worked fine at any speed with the K6, which is one of the best proves that the K6 runs reliable in overclocked condition.
To tweak the performance of the K6 to its maximum, a feature called 'Write Allocate' has to be enabled. This is meant to give you another 4% increase in performance. Most boards with new BIOSes will do this automatically, as I could check on all my test boards. In case your board shouldn't do this, there's a utility to switch on this mode manually.