I'll pipe up because I upgrade from the KM/K2000 last November.
What an improvement! Although I do prefer the size/weight of the km and the fact it can use AA batteries.
If I had to choose to upgrade today, it would be a tough call between the K-30 and the K5 - although I'm sure the K5 would prevail.. It really depends what features are important to you. Optional battery grip? Smaller size? AA Batteries? Better video controls?
I tend to purchase my bodies near the end of their cycle. Why?
Better prices and less bugs.