I don't have access to the beta versions of new Notes/Domino versions, so I haven't been able to tinker around with all the cool new things that are slated to appear in 8.5.3, but that hasn't stopped me from getting pretty excited about some of them. The big-ticket items are clear: the new Domino Data Services and relational database access (through the Extension Library, which may as well be standard) could make practical very different ways of using Domino either as a standalone data source with a different front end or as a standalone front end with a relational data source. While both types of setups are theoretically possible now, they're such a hassle that they're not worth it - but, with 8.5.3, they're almost top-tier choices for system architectures.
However, since I don't plan to rewrite my entire architecture, those new features probably won't affect my day-to-day life for a while yet. What has me most excited in a practical sense is much more lowly: being able to do a full-text search with sorted results. I've found that one of the big bottlenecks in my guild-forums app is the sheer size of the views, particularly the Posts one. I used to stuff pretty much all of the summary data into the view, but then I found that removing the non-sorted columns sped up responsiveness dramatically. That whetted my appetite for clearing out unneeded sorted columns - since each sorted column contains a full view index, having even a handful can increase the total index size dramatically. Since it appears that FTSearch's performance is almost (but not quite) as good as getting all entries by a key, I'll be able to remove the rarely-used sorted columns, speeding up all the common operations in exchange for a very minor hit in the rare case. Plus, it'll just feel good to put Domino's searching capabilities to proper use.