I hate to do this to XB1 fans but...
ESRAM creates latency in variable-environment games. Period.
It may help push HD textures better than DDR3 alone, but the data has got to be called and retrieved before it gets into the pipeline. And since ESRAM acts as a cache, it gets flushed for new data whenever repeating data stops being called (when new levels/models/art/etc... are streamed or loaded)
That creates latency, which is ultimately a bottleneck.
The only games that will benefit from ESRAM are games with mostly static environments, like sports games or racing games, where all the art for the backgrounds, player models, etc... are loaded one time and don't change during the individual games or matches. Which is why games like NBA2K14 and Forza will be able to handle 1080p/60fps on the XB1. (ie. NBA2K14 games take place in one, enclosed arena at a time, with no draw distance or atmospheric effects to create. No variable explosions, no sudden bursts of light or particle effects. Here, ESRAM works well. Same with Forza, where each race is on a single track, within a capsulated environment where the background is actually a scrolling plane, as opposed to a true 3D landscape. Again, no major particle effects, no variable explosions... all art is largely loaded one time and that's it. It’s stored in the ESRAM bank and stays there until the next race or match or game loads up.)
But in games that have big, open worlds (Skyrim, GTA, etc…
, or big MMOs (Everquest, WoW, ESO, etc…
or large-sandbox FPSes, like BF or large map CoD games, that have literally thousands of unique art assets and effects constantly being called, ESRAM will struggle because it's constantly being flushed for new data, rather than just providing the same static data. And since it’s only 32MBs, it’ll be flushed constantly, making it less useful.
That will be the limitation for the XB1 for the entirety of this "Next-Generation". The XB1 will simply work better at 720p upscaled than it will at 1080p native, because the 720p art assets are smaller.