I have had round tables for longer than I had a rectangular one and do like them. If you do not actually need that dining area you might use it as a combination room and a round dining table can be used 'a la Martha Stewart' with books on it in a room that is used as a sitting room/library/office or even a craft room.

I have a round table in my large LR that I mostly use as a desk, often with piles of books on it, but we've also used it as a game table, for doing jigsaw puzzles, and right now it's a surface to hold a Christmas vignette. We've also occasionally used it to eat at altho we mostly dine in the breakfast area of the kitchen.

I believe rooms need to be used however works best for the residents of the home, never mind what the architect labeled them.

We have the same set-up. Our formal DR to the left of the entry has a small table in the middle and one wall of bookshelves and another wall with a desk system. It's a combination library/office/kids art room. I love it. The table is covered with my kids' unfinished "art" more often than I'd like, but it's a space for them to spread out and not have to clean up all the time. The table in there is rectangular, but I'm a recent convert to the round table. We bought one for our kitchen eating area and I like it much more than a rectangle. It seems to invite conversation and the feel of family more than our rectangular one did.