I live in Germany and the midwives and docs here (we have pp insurance-covered midwife care here) are now advising that some babies are ready to start solids at 4 months. There are studies that have shown that introducing some foods early actually reduces allergies. It depends on the baby, though. My daughter definitely showed an interest at 4 months and could sit upright for swallowing. She really enjoyed her first mealtime.
The docs and midwives never once mentioned rice cereal to us. We were told to start with pastinak thinned with breastmilk or formula when we thought she was ready. After that, we were advised to try carrots, pumpkin, and potatoes (sweet and regular), then move on to other veggies and fruits. I do use rice cereal on occasion to thin the taste of strong fruits like kiwi (still a bit too sour for her, but with rice cereal she loves it) and started with that because it is gluten free. Now that she's OK with the rice cereal that is easier to digest, I generally go for spelt cereal instead. (She's 5.5 months now.)
As we felt our daughter was ready for solids kind of early-ish, we've gone for a modified baby-led weaning. I want her to eat real food, but she's too little for chunks. I carry a fine cheese grater with me and use that to prepare her food. Apples and pears are particularly good - I can make a fine "spaghetti" from them that she easily slurps, but it's definitely not a puree (and not cooked - I don't want to cook the vitamins out if I don't have to). I give it to her on a spoon, but as she grows I'll use larger graters and let her feed herself.
As for the sleeping, Lene slept longer the first night she had rice cereal, but after that it was business as usual. I don't have the feeling that it helped - she still is up every 3 hours to eat.