If you use some other type of PID, you have to be cautious of 2 things:

1) Get a PID with a "PT100" input. This is necessary to get 0.1 C accuracy (K-type sensors only do +/-1 C). Not a deal breaker, but precision is pretty important in Sous Vide so those 10ths do come in handy...

2) Get a PID with SSR output (Solid State Relay). The built in relay of other/cheaper PID's will not be able to handle the current needed to drive heaters. If you do get one by accident, you have to drive a bigger relay with the built in one and you have to modify my schematics.