I've got a 4790k @4.4GHz. I do mostly gaming and rendering. Thinking of going up to i7-7700k. Is it worth it?
Personally I don't think it would be because you wouldn't be looking at a huge jump in power (especially for the price of the cpu, new mobo, new RAM, and maybe another copy of Windows), but if you absolutely need more power, you could do it.
You could also look at chips on the X99 platform (considerably more expensive) or try out the new Ryzen chips, although I don't think you'd see a huge difference in performance with those in gaming (they'd probably put out less fps, but I imagine you'd be limited by whatever GPU you're using before you hit that cap, generally speaking). Depending on how long your projects are, they'd give a decent boost in rendering though.
Nope. The 7700k has like a 5% increase in IPC over the 4790k. If you think it's worth the $450+ for a 5% increase in performance plus some extra overclockability, go for it I guess.