Here in Canada, our official rec is 6 months, but our doctor okay'd it at our 4 month checkup. Of course, I thought he was crazy and just said - Oh, okay then
I had full intentions of waiting until 6 months, but DD started really showing interest around 5 months... I gave her a very slow intro from 5 months 3 days. Just a tsp of rice cereal once a day for a week, then increased to a tbsp... she got her first taste of peas just before she hit 6 months... I still don't push solids at 10 months. She eats like a horse most days, but I certainly focus on her formula intake to ensure she gets all she needs, since her food isn't a complete variation yet.
FWIW - My SIL has 3 kids... first was just FF from birth (milk never came in)... he started solids at 5 months. Second was combined BF and FF (low supply).. he started solids at 6 months. Third was EBF until 10 months, then slowly intro'd to solids but still BF'd until 2.5 years old. The third was BF'd the longest and intro'd the slowest... she has the worst allergies and is by far the most picky.