I've been using Rebrickable for around 8 years, and I've shared over 70 of my creations there, so I wanted to share some of the things I've appreciated about the site beyond the core features of being able to rebuild LEGO sets into new things, manage LEGO inventory, and share creations.

1. The community. I've shared a fairly large amount of content (some of it of pretty low quality), and I've always received positive feedback or tactfully worded constructive feedback. I've yet to see a negative comment on my work. It's a community of folks hanging out sharing their hobby together.

2. The set inventories. The community works hard to keep these up-to-date. I've found them to be very reliable. These are all freely available for download as well. This is a godsend to folks like me who prefer their LEGO inventory to be in a local database they can query.

3. The business model. Most features are available for free in an ad-supported manner, but users can pay for premium features and the removal of ads.