The CE pin only needs to be pulsed if the chip is operating in momentary push button mode. In this design, it's operating on levels, when CE is held low all the time to enable play and record. If CE goes high, everything stops! It is possible to add a pause mode, by taking the CE pin high during record/play. I might add that to the deluxe layout if you guys think it would be useful (can't see it myself though).
The design of the 25xx series now means that there's no longer an OVF or overflow pin. Previously this was used to reset conditions or for cascading multiple chips. With the new chips, if you reach the end of the record time, it will just stop and wait and begin looping as soon as you hit play. If you record a full 60s, it will still loop when it reaches the EOM marker.
If you don't want the pedal to go straight back into play mode when you engage it, just click the bypass switch before you hit the play switch. That will put it into standby mode (thus ending the recording), ready to begin looping when you hit bypass again. If you were really fussy about it, you could just wire up the reset pins to a second latching on/off switch and use that to start and stop things.
Robbiecm, you are correct about the switch wiring. B is the center pole of a SPDT, or one half of a DPDT.
On the deluxe layout, Mix out is the output of the ISD chip, buffered by the effects loop. Effects are wired to the FX send and returns. Mix out needs to be connected either to the MIX IN connection, to use the mixer in the circuit, or it can be wired to a seperate output. In this case, you can omit the fx send/returns. If you don't want to use the FX loop, just connect PLAY pin 2 to the MIX IN on the layout and omit the TL072 and associated components.
On a related note, I found a website somewhere where one of these loopers had been built with a pair of chips, each recording the same thing. They can then be pitchsifted and generally messed with to make some really interesting chorus/flanging and general dischord.

Nice!