Well, MidiBridge does exactly what it says it will! I just spent some time playing SunrizerXS and Alchemy from the SS25 and the response is fast and clean. Pitch and modulation work as expected. Sunrizer doesn't show the pitch and mod animations, but that would be an issue with the synth itself. There's a second's lag when you switch synths before it connects, but once connected it stays that way.
One important things to take note: on the Preferences page make sure you enable "Background Mode" otherwise your MIDI connections won't be enabled when you make another app active. It says it "uses more battery" in this mode but if you AC power your SS25, that's no problem. You also have to remember to activate MidiBridge in order for the SS25 to reconnect automatically to the other apps. It remembered my connections when I restarted the synths so config is memorized.
MIDI connections always introduce some semantic confusion as one MIDI device's input is always another MIDI device's output. In MidiBridge's Interface's page, you're presented with two columns of devices: the "inputs" are on the left and the "outputs" are on the right. But by "Inputs" the author means "where MIDI commands are coming from" which technically
is "Outputs". It took me a bit to figure it out, but it's really just a question of convention. It might be simpler to just refer to "Source" and "Destination" as that makes it clear.
All that's needed to connect the SS25 to a synth is to highlight the source by selecting it and touch the destination to connect. Do similar to disconnect. One source can connect to multiple destinations and vice versa. Open Synth apps appear as destinations too.
Each device has a Filter page allowing you to filter major MIDI events. I already wrote the author about the possibility of introducing MIDI velocity scaling on this page (these small keyboards could use some optimization...), and it's a "we'll see"
There's also a Drum Remap which may come in handy at some point, though it's currently undocumented in the beta. The Filter can be enabled/disabled globally for each MIDI device.
I tried triggering notes from my MBP running wireless using Core MIDI, but for some reason, once the session is established and once any synth becomes active, it plays a stuck note on its own and won't stop. This happened on both Sunrizer and Alchemy. I'm not sure what is going on, here; I'll have to take a closer look.
Couple of other notes: If the iOS device powers down, just turning it back on re-enables everything without issues. Landscape mode works on the iPT-4G in this new beta. There's a new "Compatible Applications" page in the new Beta, with a list of apps and checkmarks; I'm not sure why that's needed, but I'm sure we'll find out