Should I almost always use virtual inheritance?

The drawbacks are that

1. All classes will have to initialize all its virtual bases all the time (e.g. if A is virtual base of B, and C derives from B, it also have to initialize A itself).
2. You have to use more expensive dynamic_cast everywhere you use a static_cast (may or may not be the issue, depending on your system and whether your design requires it).

Point 1 alone makes it not worth it, since you can’t hide your virtual bases. There is almost always a better way.