A lot of bugs are solved on a weekly basis (see release notes). The more people that have a MSX-VR, the more bugs will be found and can be solved as long as they are reported through the proper channels 
It is quite a big project and as you know Rome hasn't been build on one day either...
If I/O doesn't work, then that is quite an impediment for a lot of interfaces, hope they add it later, it would be quite a shame to have that many slots and not be able to put hardware there, after all, if you want to just emulate everything, OpenMSX is free and you can make a quite good looking keyboard case for it running in a PI4;
Well, some work. Moonsound does. Darky, sometimes, a bit borked. Music Module doesn't. Not both mine at least...
My SD and CF failed both.
Hope they get it working reliably. 
Probably. At first it was very bothering the SD not working cause I use them on my MSXs, there are custom things and so... Then, I got used to just use WiFi and it's more handy, unless you don't want to plug the PC on. But then some USB or USB reader with SD can do, as long as it's FAT32. Good cause it's more handy, not so good cause then my MSXs can't read it.
But you can't have everything.
About MM and so... not big deal as it's emulated, but as you can't trust any emulation in the end, just in case, it's good to make the real hardware work. Well, I can, on my other MSXs. It just seemed a pity cause sure it's a matter of little fix there, as more complex hardware than MM works.
So, time to wait. No hurry.
