Well kudos for ideas outside the box and a good example of D&D creativity in general.
Githyanki IMC have always been high level 10+ encounters though, Starting characters at first level with Githyanki and intellect devourers and mindflayers seems a tad unbalanced. The railroad, of course, starts right at the beginning with the characters being infected by illithid spawn in a deux ex machina plot device setting up time constraints to uncover the entire plot and storyline before the character is irretrievably destroyed. I find it much preferable to setup a story line, and then let the players choose how to proceed, In the above example, I would make a play on the characters greed, ambition, or avarice and let them be tempted by some macguffin, only to find the angry spawning illithid. Two things with this, it's the players idea to get involved ...and everything is their fault, because none of it would have happened if they weren't so greedy/ambitious/hostile.
That said, the graphics for the game levels look reeeally good, and I like how they have picked up on utilizing more mechanics such as hide in shadows for thieves, along with a destructible environment making exploration much more interesting. All in all, so far i would rate it about a 6/10. Pretty sure the designers are going to go hog wild on the environmental variables, but almost completely ignore the transplanar elements. I wasn't impressed with the Githyanki though. They looked more like elves, and are much less mean looking than the classic Githyanki from Fiend Folio. All you had to do was just see one of those, and you knew there was going to be trouble. I didn't get the vibe from the Elfin cutekin here.
I'll be really impressed the day computer game designers come up with a working system so that wizards can create brand new spells, and new types of spells, by recombining existing spells. In the Diablo series they actually did this with magic items, and it greatly enhanced the game. I wanted to continually quest in that game to get better magic items and spell components to make better magic items.