I was going to upgrade to the 15" but... here's my story:
Love the M2 Air. Didn't expect to, but I bought it as a second computer for my den. This little machine kicks butt and so when the 15" was announced I watched all the videos and decided I wanted it.
Apple's trade was $655 and while that didn't seem too offensive (I bought mine used so not too much of a hit) I listed it locally and got a couple hundred more. I took the cash to Apple ready to buy the 15" and then... I picked up the 15" for first time in person. Uh-oh - while the bigger screen is everything I could have hoped for, this thing is quite a bit bigger/heavier than the pics/reviews make out. I was expecting love at first sight, but it definitely has given me pause and so I'm thinking about it.
In short, I somewhat regret selling the 13". Luckily this was not my main machine, so I'm in no hurry. I'll go back to the Apple Store and take another look at the 15" and then make a decision sometime in the next couple of weeks.