Door of Destinies gets its charge counters off casts, so your Door will still charge up even if a sliver or two gets countered
The negative point of this test is that if the card is extremely expensive, you won't be able to feel it in your hand, like the "Power Nine", as they are so expensive that just by having fingerprints on them, already their price can be altered
Turning off counterspells is always a bonus and sometimes vital
Mark your targets, but be sure to discuss beforehand who has what removal ready to go, lest we make some unwanted enemies
Agatha's Soul Cauldron even makes it so you can use mana of any color to activate abilities
1 Ureni, The Song Unending Power Unleashed The massive Spirit Dragon Ureni, the Song Unending is not only a beast on the battlefield, but a pretty significant undertaking in terms of mana