Having companions is a HUGE part of why I love and play cRPGs. Well-written companions with solid party interactions is a must. And party size should remain at six - yet another reason why the original BG games are awesome and the D:OS games suck.
But one thing I didn't like in BG was that so many of the companions were encountered late, and some even very late in the game. I tend to like to establish my party as soon as possible, and then after I have established my party I get very attached to those companions and don't like swapping them out for newly-met companions. As such, I end up not playing with the companions you get to meet later in the game even if they're possibly the "best" companions to have in your party.
I installed a mod to have a party of 6 in DOS2. . =))
You can take all companions in one playthrough that way, It is a tradition (also downloaded a mod to double the enemy numbers and it is still challenging).