I weigh during TOM. Sometimes I gain a pound or two, and sometimes I don't. There doesn't seem to be any rhyme or reason to it.
I do get a little disappointed whenever I see a gain, but as long as I know I've been on plan, I try not to get too bent out of shape.
My weight can fluctuate by 3 pounds throughout the week anyway, but the overall trend is down, so that's okay.