We started when DS was about 7months, he had really got the hang of solids, his sitting up had improved no end aswell. However we did eat at 5.30 most nights anyway but we had got pretty sloppy about siiting to the table, you know what its like when babies are new we didnt really get out of the habit of eating off our laps until DS ate with us. We found the quantity of what he ate went up once he ate with aswell. Yes, it was hard work (or it felt like it) to begin with but I soon we got into the routine it was lovely, dinners are my favourite part of the day the one time we all stop what we are doing and arfe together. Also afterwards while I clear away it gives DH chance to spend with DS too!
HTH
Nome