GameDaily have a Mass Effect preview up, as one of the hits of E3 you know there will be praise, but not all praise.

It's also worth noting that Mass Effect is an enormous game. The space station that serves as the central hub, the Citadel, is thirty miles long! And on top of that, there are numerous planets to visit that, once landed on, can be explored either on foot or inside of your all terrain vehicle that can be upgraded (adjust horsepower, grip). However, there doesn't appear to be any space combat, so don't expect wild firefights en route to the next planet. The game has a galaxy map, and it appears that you'll just select where you want to go, but you will encounter asteroids and derelict starships. There's just a tremendous amount of stuff to do and things to see, and if BioWare has its way, there will be downloadable content, though I'm not exactly sure what that means. It's entirely possible that the game's developers will be able to add new weapons, costumes, and missions, but whole planets may be out of the question.