For those who are getting a chance to play with the 5.4 release, I'd really appreciate if you took note of any performance issues you are still having, and in particular if you can accurately describe the scenarios under which performance degrades. I only have limited time and resources to devote to testing, so detailed descriptions of where, when and under what conditions you see poor framerates would be useful. If you can share a world file and the coordinates where it happens, so much the better.
There are some things we already know will contribute to low framerates, described below:
The longer your view distance, the more stuttering you will see when moving. While we have greatly improved this, the simply fact is that long view distances increases the number of chunks which must be instantiated exponentially (roughly as the square of the view distance.) On my personal machine (3.2ghz, 980Ti, 32gb ram), I see good consistent performance at about half the maximum view distance. Longer distances will maintain good framerates due to other improvements, but the frames will start to stutter more.
The client does not purge unused chunks from memory yet. If you go on a long sojourn, memory allocations will accumulate. While this memory isn't bad per-se (we don't actively access it if the chunks aren't actually in view) it can put pressure on your machine as a whole causing the OS to start paging. This can severely reduce performance. We will be addressing that in a future update.
While I haven't investigated it personally, I suspect there are circumstances where significant data must be transferred from the server when things get updated - especially in busy cities. If you see this behavior, I'd like to know more details. These can cause frame stutters for two reasons: 1) if we have to create a lot of new objects to display and they don't benefit from the new pooling optimizations, Unity can choke a bit, and 2) many of these kinds of updates result in lots of memory allocations which the game must then clean up - and those cleanups will directly cause frame stutters.
Another possibility are actual memory leaks - objects we create but never destroy even though we don't need them. If you regularly encounter a situation where you are staying within a relatively small area but your memory continues to grow without bound, we'd like to know about it.
Again, thanks to everyone who is testing and special thanks to those of you who have provided us with bug reports and good repro scenarios. And as always, thanks for your patience and continued support. :)