Yes, the ever-present seating chart. To assign guests to a table or not assign them? I have created for your enjoyment a pro-and-con chart for using seating assignments.
Pros
Cons
So the moral of the story? I'm afraid I don't have one. I will say that the majority of the time, even when the servers have to serve the tables, it is easier to let the guests find their own seating arrangements. The guests who care where they sit will take the effort to find seating early. This way, people can sit wherever they want and with whomever they want. I would still recommend reserving enough tables for extended family, because they tend to be the group that only knows a few other people. And if you just leave a few tables reserved, you don't have to worry about sticking family members together who aren't talking; they can take care of it themselves.
If you're going the serving route where the servers need to know beforehand what guest wants what meal, you can still make it easy for them. Like table arrangements, simply make place cards for each guest and use different colors for each dish. For example, if you're serving fish and chicken, use one of your wedding colors for fish and the other for chicken. And if you include dietary arrangements or kids' meals, you can have colors for those, too. The guests can find their name before they enter the reception hall, then the servers can check the colors before they serve the meals and know which dishes to grab.
Now, before you throw away any intention of using table assignments, know that guests will still appreciate the effort you put into selecting your table. There were weddings I attended where we were given seating arrangements that were created with great thought and care, and because of that my husband and I didn't have to stress about finding seats with people we knew. So if you really want to do assignments, go ahead. I won't stop you.
Tip: Though it may seem easier to utilize large round tables, it's better and more enjoyable for your guests if they sit at smaller round tables or rectangular ones, because it keeps them closer to each other and makes conversation easier.