1080i vs 1080p Looks so much different..I think

[kupe]

Blu-ray newbie here so enjoying and trying to learn from all the expertise here!

So, we have a brand new Sony Blu-ray player BDP-S380. It's connected by HDMI to our 4-year old Sony Bravia 32" 1080i LCD. When I switch input to the Blu-ray, the TV says it is sensing a 1080i signal (just as it says, for example, 720p when I switch to our Apple TV.)

I guess I'm still not 100% clear on what resolution is actually being sent to the TV when playing a Blu-ray disk in this setup. Is it, as the TV senses, 1080i? something else?

I ask only because we're not "blown away" so far by the difference in picture quality between an up-converted standard DVD and a Blu-ray disk. I haven't yet had a chance though to compare the exact same movies on DVD and Blu-ray, but that is my plan if I can get to it this week.

Thanks!

Kupe