Yay, finished the game at exactly 15 hours and 100% with no walkthrough help...A very satisfying final boss followed by a satisfactory ending...
Don't read unless you've seen the special 100% ending! I liked the close-up of Samus' face; Retro did a good job on it...Oh, and what the hell was with the "cliffhanger" ending, Retro!? Either they want to get back to Metroid as soon as possible or it may have to do with the elusive Metroid Dread, which they teased at in the Metroid containment area on the Pirate Homeworld!