The ending of Deathly Hallows Part 1 comes down to two beats: Dobby dies in Harry's arms at Shell Cottage, and Voldemort breaks into Dumbledore's tomb and takes the Elder Wand. Together they show what the friends have lost and what the villain is about to gain.
Dobby's death matters because the character has a long arc. Toby Jones's house-elf first appears in Chamber of Secrets (2002) warning Harry not to return to Hogwarts, so his return to rescue the prisoners at Malfoy Manor closes a loop that began eight years earlier in release terms. The rescue itself is tightly built: Bellatrix is torturing Hermione, Dobby appears, the prisoners are freed, and Bellatrix fatally wounds him as they escape. In my opinion, the choice to have Harry dig the grave by hand at Freshwater West is the film's quietest and most effective moment, because it shows grief without a set piece. Earlier films in the saga, such as Order of the Phoenix, tend to answer loss with a large magical duel, and this one deliberately does not.
The Elder Wand ending is about stakes. Over the preceding hour the trio destroy the locket Horcrux, with Ron using the Sword of Gryffindor after pulling Harry from the frozen pond, and they hear Xenophilius Lovegood describe the three Deathly Hallows (the Resurrection Stone, the Cloak of Invisibility and the Elder Wand). Voldemort, by taking the wand, moves a step ahead of them. It could be argued that the film ends on its villain rather than its hero for this reason, and that Part 1 is built as a first half rather than a standalone story.
That structure has a production explanation. Executive producer Lionel Wigram suggested splitting the final book into two films, and Parts 1 and 2 were shot back to back from 19 February 2009 to 12 June 2010, with one reported $250 million budget covering both. Because the two films were planned together, Part 1 can end on an unresolved note, with the Horcrux hunt and the fight over the wand left to the 130 minute final film. Compare that with Half-Blood Prince, which sits at 153 minutes and was shaped as a full instalment inside the school year structure. Part 1, at 146 minutes, borrows its tension from the road instead, and its ending is a setup in a way no earlier Harry Potter ending was.