Almost my entire apartment is IKEA. I used wood glue at every joint and everything is still solid. It even survived a move!
IKEA is great. Cheap, and looks good for a long time. Don't expect that it will hold up if you move it around (though you can be lucky, just don't count on it) but if you don't expect to move it then I'd highly recommend.
R&F is expensive stuff. I really like their solid wood frame furniture (bed frames, dressers, desks, etc) but I've only ever bought them second hand on craigslist- at 10% of the retail cost and in nearly perfect condition - and they've held up for 10+ years so far. The folks who buy this stuff new tend to live in nice neighborhoods and get rid of it when they redecorate - not when it's ruined.
That had nothing to do with couches, sorry. I wouldn't buy those second hand (upholstery is different from wood). I got mine at a department store back when those were a thing, paid a lot, but still using them, so I have no other experience to share. Except that everyone says to buy Natuzzi
