I have a Startled Awake that is frequently combined with Decimator of Provinces to give it Haste. However, most of the time, Startled Awake won’t attack the turn it comes into play, thus negating the whole point of haste. When the Decimator comes into play and gives Startled Awake haste, the dark cloudiness of summoning sickness goes away, but still no attack. Startled Awake will start attacking as normal the next turn.
I say “most of the time” because I have twice seen a hasted Startled Awake attack on its first turn.
Thankfully, this glitch hasn’t cost me any games yet.