I absolutely love the idea of a stronghold but it's quite underwhelming. Like, for instance, I was seriously disappointed when I found out the sleeping bonuses for various improvements weren't cumulative, and that resting at my stronghold is either for immersion or immediate necessity.
One of the things I always crave in various games is the actual feeling of claiming land and lording over it. I quite enjoy how you have petitioners and various guests staying at your castle and I'd love for Obsidian to expand on that, allowing more actual control over your lands than just arbitrary improvements. Also, I think it would be swell if they decided to release an expanded stronghold function with the expansion pack, that they'd include it in the base game as well (on account of not splitting their players between those who will have more fun with the same mechanic and those who won't).