-64bit and 1gb ram - as the 64bit OS used a lot more ram than 32bit, very little left to work with. This meant unstable OS, crashy apps, and constant refreshes. Listen to a podcast, pause it with Control Centre (or whatever it was called back then), do anything else, press play in CC again and, oops, Podcast app flushed, music starts playing. Equally, partially write a forum post or equivalent, leave Safari to do something else, come back, oops, page flushed and refreshes sans the text you’ve typed. The painful workaround was c&p everything before leaving Safari etc.
-Plasticky feeling screen versus the glass of iPad 4 and iPad 3, less vivid colours.
The iPad 3 rightly gets panned for it’s launch time relative to the 4, and it was slow and heavy BUT it worked and was stable as it was 32bit & 1gb RAM. In hindsight I of course wish I’d waited for the iPad 4, but nonetheless I enjoyed the 18 months with the iPad 3. The iPad Air 1 went back within 14 days. Perhaps later iOS updates mitigated it somewhat, but I wasn’t prepared to take the chance, and there’s no escaping the fact that 64bit and 1gb RAM never should have happened. Had a similar experience with the 6 Plus, the worst iPhone I’ve had by far. The iPhone 3G was crappy in hindsight, lousy battery and splintered back, but it was great during the time I used it.