I don´t know what the big deal is (apart from ... ahem ... change
Coins are practical and I´ve never had a problem of "too much change". You just spend
it - that´s what it´s for!
The old Mark coins were a little inconsistent in size and colour, but the new €uros are rather systematic and easy to use:
Cent coins: 1, 2, 5 (copper), 10, 20, 50 (golden)
€uro coins: 1, 2 (bi-colour golden/silver)
€uro bills: 5, 10, 20, 50, 100, 200, 500 (individual colours)
Both coins and bills are ordered by size within each category.
I can´t say, of course, how big the transition pain might be in the US, but it might be a good idea to make the money systematic and consistent in one jump.
It can be done, and I think it´s worth it.