Just got back this past weekend. We knew the max hand luggage weight was 5 kilos so we ensured on the way out it was under. It was never checked. On the way home we didn't bother to ensure it was under, as we assumed it wasn't enforced, just as well it was under the limit because the weight was checked and most definetely enforced. Out of the US, while waiting in line to get through security, there was an official going along asking who had any liquids. Those who had, he checked the product and if it was ok you kept it, if it wasn't it was chucked. My son's liquid paracetamol was fine, however he wasn't concerned with what it was, more that it was under 50ml. Drinks were chucked (apart from baby stuff), but most toiletries were ok (apart from my mother's who had aqueous cream in an unmarked jar). When the official through the lines was happy with the liquid product, all you had to do was put it in a bowl they provided which went through the scanner. All food products I saw were fine (still had to go through scanner), but I only hard, dry food (am sure moist baby food would be fine). Once we were through security, I realised I forgot to declair my son's suntan lotion which was sitting at the front of his transparent bag. It went through the scanner, so they must have seen it and not worried. They were much stricter then the UK, with making us take all belts and shoes off, and were doing more random checks, but this was generally not a problem. Once through security, you can buy anything (drinks, perfume, toiletries) and take it them on board. We took four bottles of water because our outbound flight had run out of water!
There was no second security screening like we got on the outbound flight (from the UK). Hope this helps. If you want any further info, I would be happy to help.