Can someone tell me what was good about The White March? I didn't bother playing it because I didn't want to play the main game again.
Improved encounter design. Still too much filler trash combat, but sprinkled here and there with some actually challenging fights.
They've tried to do something different with the Soulbound weapons, and while they are a good idea in theory - it relies too much on pointless grinding to be fun.
A lot of new content, including an entire quest, has been added to the Keep. The place still doesn't feel like you really are a Lord of an impressive and important fortification, but at least now it isn't entirely pointless and boring.
The new NPCs are nothing special - Zahua is sorta interesting, the Devil of Caroc is nothing special, and Maneha is the single worst NPC in the entire game.
With this expansion, Obsidian has finally started properly tying quests to your special Watcher status, so expect a lot of opportunities to use your powers in quests and conversations. Also, there are many more CYOA screens, I think it was said somewhere that there are more of them in TWM than in the entire game.
Besides all that, there was a big patch (3.0) which changed many things about the game, so if you've enjoyed PoE at all, I reckon you should probably try it with TWM, at least to see what has changed. Even people here who fervently dislike it can't deny it's changed a lot for the better.
Still far from perfect, but a very different beast from back when it was first released.