I did nearly the same thing, except I went to a Best Buy on Friday and had them pricematch the Amazon promo. I came from an AT&T GS2 (the i777), and this thing freakin' flies.
Also, as much as I was flashing ROMs on my S2 (I tried SHOStock, but realize I really didn't like Touchwiz; and cycled between CM, AOKP, and then PACMan before getting the HTC One), I'm staying on Sense for now. I actually kinda like Blinkfeed, and Sense is a lot more usable than Touchwiz for me. It was a bit weird to go back to 4.1.2 JB after using 4.2.2 ROMs so much, but it's not been as painful as I thought.
Keeping my semi-busted (I don't think anyone will really buy a phone that doesn't have a working power button) as an absolute emergency backup, or a smaller-than-tablet game device for my kids. Though, if I were to sell it, I would wipe dalvik, cache, and for extra measure, format the internal SD card to get rid of other stuff (downloads, leftover folders, that aren't touched by a /data or /system wipe that a factory reset does etc). I would then reflash a ROM from the external SD card after wiping the internal one.
Thanks for the pointer to the Play Store credit promo.