Actually big enough for 4
*UPDATE* Have now used this tent for 18 months on several trips in all conditions since my original review.
I LOVE this tent. It's one of my favorite pieces of outdoor gear. I love it so much I came back to update this review! It's been through several days and nights of steady rain and come out perfectly dry inside. Totally bombproof construction . Zippers are solid even after being manhandled repeatedly by kids. Plenty of room for me + 3 adults and we've even done 2 adults and 3 small kids. Condensation is minimal even with full occupancy and fly pulled down drum tight. The gear pockets on the sides are such a great idea.
OK - so this is one of those reviews that starts out 'I have only set this tent up in my yard but...' This tent REALLY can fit 4 people side by side (not alternating head to toe) comfortably. I know because this afternoon I made my whole family stop watching the tube and come out in the backyard and lay down inside it in their sleeping bags. At least my youngest thought this was fun. Anyway, there was PLENTY of room for the 4 of us without rubbing elbows. The vestibule (and the car) will hold most of our gear, so as long as its just sleeping bags and pads, this is perfect for a family of 4-5 depending on kid size. 4 adults could fit comfortably.
I debated quit a bit between this and the BA Big House, which gives 65 sq ft floor space compared to the Limestone's 60, but I'm pleased to say 60 is enough. Great job Marmot!