If you haven't been following the news until recently, be aware that this release contains a number of updates to both the input and sound code. The sound code in particular bears mentioning because its new behavior has tripped up a few people. Sound output is now exclusively controlled by the emulation, not by the OS layer. This means that it is very important to have accurate timing and throttling. Because of this, the throttling code has been rewritten to be more forgiving of "hiccups" and other anomalies.
One non-obvious side effect is that if you are running your games with -triplebuffer or -waitvsync on a system with a 60Hz video mode (like most LCDs have), and you are running a game with a framerate greater than 60fps (any of the common older Namco titles will do fine), then you will experience sound hiccups unless you enable a little bit of frameskipping, either automatic or a frameskip of 1. This is because you are hard-limiting the game to run at 60Hz due to your monitor's refresh, but it needs to produce more than 60 frames per second, so you are always running behind the emulation.
On the input front, Derrick Renaud has done a lot of work to try and normalize the behavior of analog inputs across the project. He has fixed and tweaked quite a number of analog controls in the system. Because of this, you may find that you need to throw away your existing calibrations and re-calibrate with the new settings. The advantage of the new system is that it fixes a number of inaccuracies in the behavior of the controls and allows games to have more flexible options when it comes to mapping controls on your PC to the controls the game used.
In addition to these changes there are quite a lot of new unplayable Bemani games that have come out of the woodwork over the past week or so, as well as an implementation of the long-desired (by pinball guys anyway) BSMT2000 ADPCM code. For this release I've also enclosed some regression testing tools I've been using for the past few months to help catch problems introduced between versions of MAME. You can see an example of the progress between 0.112 and 0.112u4 by looking here. Note that there are still a few glitches in the system, but I felt it was worth providing the code.