Well, it's fun to have the ME universe back, but they changed almost everything. In most cases, not for the better. The story is OK, not nearly as interesting as the first. There are too many new characters who replace most of the characters from ME 1. All of the old characters make appearances, but only two play a actual role. One of the only positive changes is the new Normandy.
All the hype about choices made in ME 1 affecting this game was pure BS. Nothing you did in ME 1 will affect or change the outcome of this game. It only affects a few cut scenes, random encounters and messages. The Ashley or Kaiden decision from ME 1 only affects who will appear in one mission which has absolutely no impact on the game.
It plays like a on-rails shooter than a open world rpg-shooter hybrid like the first. Combat is totally different and now 1,000 times harder. The "improved" cover system is total crap. So frigging buggy. My character was constantly locking and freezing going in or out of cover so I repeatedly had to load the last save and start over. They removed all of the open world / sandbox features. You can't just explore planets and locations like you did in ME 1. Small spoiler... the mako is gone. You can only scan planets which is mind numbingly boring and repetitive. When it does allow you to land on a planet, it's all on rails. You have a start point, a end point and that's it. No exploring, no wandering. After you explore complete the missiion, in most cases the planet or location is locked out for the rest of the game.
Overall... it's pretty disappointing. It's not a bad game, but it's nowhere near as good as it should have been. Way too many changes that removed or complicated everything that made the first game so good. Now it has more in common with Army of Two than ME 1. I'm sure EA forced all of these changes on Bioware. It feels and looks more like a EA game than a Bioware game. Which is just sad.