American Leather has the best rated sleeper on the market for comfort. Also some of the less expensive sleeper sofas are offering air mattresses inside the mattress cover. They are quite comfortable now.

this is going to be my main sofa and hence debating whether to get a sleeper or just a nice couch and use air mattress for guests! can't decide.

Excellent point about getting up from air mattress - they can smell awful too, even after some airing out.... not extremely comfy

Go with the sleeper sofa with an air mattress. I bought a sleeper loveseat with an air mattress and it is amazingly comfortable. Very easy to blow up and release the air. The best part is you don't feel any metal bars and don't get the creased mattress that happens with traditional convertible sofas - very uncomfortable. I have had mine for 4 years and it has stayed comfortable.

Check out The Sofa Bed Store - USA if you are in the States, or The Sofa Bed Store - Canada you'll find sofa beds that don't look like sofa beds. Your guests will sleep on a 7-10" thick premium mattress and feel just like they slept in a bed. Free shipping (and free returns if you aren't happy). If you can avoid it, don't put your guest on a blow up mattress, they are the worst!

Thank you all.

Try Mitchell Gold Bob Williams. It is not only the sofa that is important it is the mattress. Room and Board has also great contemporary options.

Definitely avoid an air mattress! My parents bought one for when I visit them and it feels like I'm sleeping on a slope (which I'm not). It wasn't a cheap one either. I always end up just sleeping on the couch because I can't stand it.