I also am curious, what equipment are you running in conjunction with your 1080i... dish, cable, dvd?
I have all 1080i plasma's and I run Dish Networks HD receivers, and upscaling is done through them, and the PQ is freakin awesome... When I watch Sunrise Earth on Discovery HD, It looks so good, im not sure what the hurry is for 1080p, but alas when it becomes more the norm, I will fold and upgrade.
Even my old xbox upscales up to 1080i and I think it looks fantastic.
If I were in the running and had to have 1080p upscaling unit... I would go with Mazers suggestion of the Integra.. hands down the best product out there right this minute... Of all the receivers I have seen they are already going to be outdated this year... get a dedicated Pre-amp and go seperates.