Whether you are a new or returning Specter this is a great pick up to play.
All three games are pretty much as they were in the original versions, but with some updates to the graphical fidelity. This is for better or for worse, that's for you to decide, but for me it's welcomed.
Mass Effect 1:

• Game play is a bit outdated still, especially compared to 2 and 3, because of no game play changes
  
• Game is just as it was with nothing of importance missing as far as I could tell
  
• Story is just as great as I remembered

Mass Effect 2:

• No noticeable changes compared to the original version
  
• Save data form 1 carries over without any issue

Mass Effect 3:

• Some minor stuff is un-noticeably missing, but it's stuff that I forgot even was in the game and many didn't care for
  
• All "good" dlc is included, with said exception above
  
• Story is unchanged as expected
  
• Story progress does carry over from 2

Overall Gripes:

• I wish I didn't have to install all 3 games at once as it takes up a notable 100 so odd GB of drive space

Overall Passes:

• Load time aren't too bad with the old elevator load traps not taking nearly as long as they had in the originals