Don't think that's true. I didn't even do a hard reset. I was just too happy to finally get my usb cord in i forgot all about it lol. I didn't even back up my stuff.
You start out with a lot of ram, which didn't matter much as you lose like 13mb a few hours later, but the phone overall feels much faster still. Screen rotation is like instant. The browser loads even faster. Though i still like opera 5 better because of tabbed browsing. Also for the music player, seems that the overall speed helped it out too. Normally when i listen to music for a long time (an hour or more), when you unlock the phone to look at the player, the information on the player would freeze up. I have to switch to home then back and it's normal again. Hasn't happened since i did the update yet. The gallery seems faster at opening thumbs as well. Usually for me it would just load up whatever you see and when you scroll down, you'll have to wait. Now it loads a majority of it (can scroll down like another pagw and a half), then rest you have to wait a little.
Anyhow, that's what i've noticed so far based on the things i used the most.