I switched both my kids to a sippy very early (4-5 months) as they were not happy with even the fastest flowing nipples. If they hadn't have been unhappy about it, I may never have bothered until they were older. As for solids, we did pears from about 5-5.5 months as "breakfast" and started addding lunch a couple of weeks later and supper a few weeks after that. I think by 7-8 months they were on 3 solids meals a day.
We had to add some prune juice for Spencer to keep her regular, but I think that had more to do with the hidden milk in my diet when I was BF, because once she was on soy formula and just fruits and veggies, her bm's were just right.