Hey piizzadude, thanks for chiming in, but let me try to clarify things for you, and fill you in on something I hope you never have to deal with...
First, I didn't mean to denigrate the fine work of all the custom ROM builders, sorry you misread it that way. Note how I put the custom in custom ROM in quotes? Because it's NOT literally a custom ROM, nor is it stock. It's a leak, and I said as much. In the future, I'll refrain from using custom in this manner, as I realize many may not comprehend such subtlety.
It's splitting hairs to define this as an app issue or a ROM issue, because the fix can be implemented on either side. The problem is that MLB At Bat is very particular about what devices it works with at all, and of those, which support live video (a different problem). They put restrictions in the market as to what devices and OS versions they work with, so if your phone doesn't meet their criteria, the Play store will show it as not compatible. So, the two ways of fixing it are (a) have MLB change their criteria, or (b) edit your build.prop so that it matches their requirements.
When I had a DROID Charge, I installed some of the leaks that Team Black Hat procured. This would typically render MLB At Bat 11 (last year's version) unavailable, due to this mismatch. As I do now, I then had TiBu backups that I was able to restore, which worked, but I couldn't get updates on my Charge, even though I could keep getting them on my old OG DROID! There were several places you could find the necessary changes for build.prop, which others, who didn't have backups, would use. Fortunately, over time, MLB would change their app requirements to allow the Charge to get the updates, and all was well.
Note that this wasn't the only app that was rendered unavailable by those leaks; there were several game apps that were affected the same way by the Charge leaks. I don't doubt there are also other apps so affected by the Rezound leak as well.
For MLB At Bat 12, this problem has been hitting non-VZW gnex users, too, when they got updated to 4.0.3 and 4.0.4. Hrm, maybe that's the mismatch, the OS rev...
In any case, I'm happy to report that, as of today, apparently MLB made an update, as now I can see it in the market! If it was the acceptance of 4.0.3 (which is what the leak is) and 4.0.4, then maybe that's it, and as such the gnex users are in luck again (it worked for them with the earlier release of ICS, just as it did for my Rezound prior to installing the leak).
One more thing--when I first bought this year's version of the app, live video wasn't supported, and the Rezound wasn't listed as "supported" (which literally means live video support). I complained to them, and after a short while, it started working--yay! At that time, they still didn't list the Rezound as supported, but eventually they fixed that.
And now it's all 100% good. Until the next release, maybe.
Best,
LDog
PPS--
Yes, that xda thread is one I was referencing; I'd tried some of the things mentioned there and elsewhere, too. I've posted in that thread today that the Rezound is now good with the leak (and possibly any other ICS ROMs that were having issues).