Overall I think this sleeper sofa is fantastic. It’s very firm, but not in an outright painful way even when sleeping on the seam. It has a high quality appearance, the material is very soft, and I (5’1 woman) was able to assemble this fairly easily without needing extra tools. 

Flat I’d say it’s around a twin size mattress from arm to arm with the chaise lounge attached. It’s perfect for me, but will likely feel a bit small for most. Love the adjustable back support options, although sometimes it takes a few tries to get it to lock into place. Lastly, the lounge has a large storage section that works great for storing bedding (pillow and all) if you do treat this as a bed. Worth the money for sure.