If your response is to me, it will noticeable be when... a person loads a 720p H@L5.1 h.264 file onto a Tegra 2 device. It will skip and be unwatchable. This is the de facto standard, well... at least in nefarious places

.
The technical differences are:
Baseline Profile Support only (ala Tegra 2) means:
- No CABAC entropy coding.
- No B frames
- No 8x8 transforms (DCT)
- No Weighted Prediction
I call it a regretful omission but Nvidia's marketing types may disagree (even saw one rep trying to PR this in another forum!), but I believe the engineer tasked to this department got a lashing from someone, or at least I hope!
I'm trying to find a vid example for you, but can't seem to atm. But essentially, even an iPad 1 can play back HP vid fluidly, whereas Tegra 2 (even w/ dual core cpu) can not.
This is my deal breaker, because if I'm going to have an HDMI port on my phone, it ought to be used to the A/V fullest. Shame about these devices still having 32GB microSD card limitations though... wonder if a 64GB would work.