I only bring this up, because I have roughly 110 apps on my S2 and only 3 of them are phone apps (those being MMA Underground, Target and Speedtest.net). However, all 3 look fine and aren't pixeled out like I would get on an iPad. All 3 are still perfectly usable, you just have to be in portrait mode.
If this is the average use case, then approx 2% of apps aren't optimized for Android tablets. Is this significant enough to proclaim that app optimization is a hindrance for Android Tablets? Also considering the apps still look and function fine, albeit in portrait mode? IMO, the answer is no. BTW, in my particular use case, 1 app out of 96 apps on my iPad air 2 was not optimized. So, slightly over 1%.
If Google this year releases a good Nexus tablet, I could see myself exploring Android tablets...
I'm content with my iPad Air. It's mostly just a media, game, and web-browsing consumption device for me. For the simple things, the iPad and iOS are great.
I'd be interested in exploring a well made Nexus tablet if one existed later this year...