I just received my i7/8GB/256GB MBA through UPS today, and I'm doing some intensive installation tasks now (including installing games through my virtualized bootcamp partition); I can already notice a fairly substantial difference in the heat between the baseline i5 MBA 2013 that I had picked up from the Apple store to try out.
I was pleasantly surprised by how cool the i5 was, and was happy about being able to use it on a bed/couch while the unit still remained cool (granted, not gaming, but kept it's cool with streaming flash video).. already with this i7, I can feel it getting certainly noticeably warm on the underside, borderline uncomfortable on the lap, and definitely uncomfortably hot in the very top part of the keyboard by the screen (fortunately there's no reason to really touch there..).
I'm a little discouraged by this, as I'm not even 100% sure I need the i7 upgrade, considering how performant the i5 ended up being in most cases. I just figured if I was upgrading the RAM and HD, might as well get a faster CPU as well. It's possible the extra stick of RAM is partially responsible as well. Now I'm somewhat regretting the decision.. I was quite fond of the cool temps.. that being said, I don't really game from the bed/couch, it's possible things will still be manageable in my use cases.
Granted, the i5 still got relatively hot and the fans kicked in when gaming as well. But you could barely feel it on the underside, just along the top, where it's insanely hot on the i7 version.
Anyway, TL;DR - yes, seems like the i7 does run quite a bit hotter.
[updated with a screenshot of temps from iStat Pro.. maybe someone can post temps of an i5 doing intensive tasks]
