We tried business class for the first time ever coming back from LA with BA, it was DH's and my 50th and the kids had just done GCSE and A-level and i just thought "feck it, you only live once". It was a night flight and I chose to do it on the return leg thinking we would likely get some sleep with the lie flat beds but I barely slept a wink. The vibrations and noise from the engines were awful. I was far too hot, and thirsty, but didn't want to disrupt everyone in the middle of the night calling the crew for drinks.
The lounge in LA was absolutely lovely, though! A total peaceful haven, with nice food and drink, and so much space to find a quiet spot. It was really chilled. The food on the plane was ok but my body clock was totally out and I didn't want breakfast at all when they offered it in the morning but I felt that as we'd paid all that money we should try it. Ended up trying to force it down so left half of it. Waste of money. Lots of people didn't bother with it at all and just stayed asleep.
The business class lounge at Heathrow when we landed was a disgrace (we were flying onwards to Manchester). Far far too many people. There were tables that hadn't been cleared, we struggled to find a seat. It didn't feel premium at all and was such a disappointing experience. Also the onward flight to Manchester from Heathrow was pointless being business class. We had an afternoon tea virtually flung at us as there wasn't enough time. It was rows of 3 and they just kept the middle seat free and that was our "business class"!
The best thing about it all was the lounge at LA and the privacy of your own little space on the plane. Being able to lounge right back to watch TV was nice.
If I ever did it again (for a special occasion) then I would research carefully about whether the lounges included felt luxurious and exclusive and peaceful enough (I would NOT include Heathrow in this bracket). I'd also choose a day flight actually, contrary to what you'd think, as I think you get more out of it. But I am a VERY light sleeper, so if you think you'd get the benefit of the beds if you're a deep sleeper then it may be worth it just for that.