Fixes
Features
strings
user lists
objs
mobs
areas
images
appearances (an internal type)
unique overlay/underlay lists
The number of cache objects (files) is also slated to increase, but so far the only change to those is that they are now internally represented by 4 bytes. Code to actually increase the limit proper will be added in a future release, but it's a relatively simple change now.
The old 2-byte limit still exists in Dream Maker. Your projects still can only use up to 64K unique strings, unique types, etc. This is to maintain compatibility with all the code that reads and writes DMBs and the code for compiling and executing procs. Note that this could be a cause for confusion: your projects still have the same limitations at compile-time; it's the runtime capabilities of the engine that are expanding, so that's good for dynamic worlds and anything that loads/saves maps like with SwapMaps.
As a result of this major upgrade, the server-client messaging protocol had to be altered. Because servers broadcast many of their messages to all clients, a 433 server cannot communicate with older clients. A 433 client however should be able to connect to anything.