K-3 has 92 weather seals, up from 77 in the K-5 (and 81 in the K-30 and K-50).
For comparison, the Canon EOS-1D X has 76 seals.
On another note, battery life (without flash) has gone down from 980 shots to 720 shots. This is well below average for this class; extra batteries are a good idea. The K-3 accepts the same D-LI90 battery as the K-5. A new AC adapter K-AC132 is available; the older K-AC50 will not work. (Extra D-LI90 batteries are cheaper than their C&N counterparts: the D-LI90 costs $40 but the Canon LP-E6 costs $60 and the Nikon EN-EL15 costs $55.)
Frankly, this isn't an issue for me. I rarely exhaust one battery on my K-5, let alone both. When I get the K-3, I will probably get the D-BG5 and an extra battery to go along with it, and I will have four batteries to work with.
--DragonLord