Invaluable. especially re screw lengths-though how you tell a 2.3mm screw from a 2.4mm screw is a bit of a poser. Unsoldering the battery before folding the logic board out of the way worked for me. Unsoldering the old battery connections was difficult, though, as the battery fitted had the connections apparently covered in plastic. Didn't find any problems using leaded solder - certainly in UK it is allowed for repair work.