D4s are annoying. They're the only die without a top face, so it's hard to read the number, and since the faces slant inwards it can be hard to pick them up.

On the other hand, it's satisfying that the typical RPG dice contain the 5 platonic solids. If I had to play a game where a D4 was used often (unlike in say D&D where it's rare), I'd probably go with one of the alternate D4 shapes. Even if you prefer platonic solids, you can just use an 8-sided die and renumber 5-8 as being 1-4 again.