So…
Can someone help me verify the considerations necessary in firmware for x3 pro running on 24v with kraken?
Hot ends require 12v, so pwm max is cut in half
Do I need 12v for thermistors or can I use different/scaled tables?
Steppers should be happy
Need to verify I should add male pins to motor drivers- for i2c connection current limit setting?
Heated bed is rated for 24v
Ready to do wear in!
As power is voltage squared divided by resistance, if you double the voltage power is four times what it was before. If you do PWM 50% you are still delivering double the power to the 12V heaters now. Whether that is causing you problems or not I do not know, but if you want to keep the power the same your PWM should be 25% instead.
Steppers will be more than happy but if you have polyfuses in your electronics watch out as most of them are only rated 12-15V.
I thought thermistors were driven from logic voltage (e.g. 5V) so shouldn’t matter. I guess check your 5v regualtor can handle 24v and is properly heatsinked if its a linear regulator - as it will get a bit hotter. Do you have fans? might need a 12v regulator to drive those.
My recommendation is buy a 24v heater cartridge and components. They are cheap, and less chance for a horrible meltdown failure. Same with the fans. Just my 2 cents.
I second the recommendation for 24v heater cartridges. Had a bad experience once… 
Agreed, do yourself a favor and get 24V cartridges I’ve seen a 12V cartrdige literally get red hot myself… Also the auto PID autotuning seems to struggle when I ran a 12V cartridge at 25% PWM. Here’s a guy at AliExpress who sells 5-packs of 30W 24V catridges for $10:
http://www.aliexpress.com/item/5PCS-24v-30W-Ceramic-Cartridge-Wire-Heater-For-Arduino-3D-Printer-Prusa-Reprap/1906915702.html
Thanks for the info guys - remembered the pwm reduction wrong. I’ll order the cartridges and double check the regulator. Fans I’ll power with a step-down power supply I’ve used before - 3 Amp capacity: http://www.amazon.com/dp/B009HPB1OI/ref=sr_ph?ie=UTF8&qid=1413867722&sr=1&keywords=step+down+power
If you did get new fans I recommend these http://www.ultibots.com/40mm-fan-kysan-tf4010-24h-s/
Ultibots also has 24v heater cartridges.