I personally think you'll be let down or impressed based on your expectations. Unfortunately through advertising and other forms you generally are a little more built up than you should be.
I think the ride is amazing. However, I was still let down a little. As magnificent as it is, Im simply saying that my expectations were thrown a little higher than i felt they should have been. dont believe me? Just watch a Disney video promotion on the ride.
I think the technology is great. However I dont feel it's realistic like they claim it to be. The G's are less than that of many coasters. The ride system is not unique to Disney. The actual ride system was mirrored from other world attractions, which is a problem many disney purists had with the attraction's design. Also, as much as I love MIssion space, I still think Universal's Islands of Adventure's Spiderman ride is still more technologically advanced than Mission Space. I dont like Spiderman as much but when you remove your bias, the Spiderman ride is more technologically advanced in itself.
So while I will say that it's one of my favorite rides and I just love it, I do think it's overhyped, along with Soarin.