This is a lovely review by IGN:
Elizabeth Mitchell is bringing another type of evil to the series with her performance. Regina as the Evil Queen is bad with flair, Pan was calculating, Zelena was deliciously over the top, but the Snow Queen? She’s got a sort of quiet terror about her. She’s calm as she goes about her horrible business; she could fit right into a psychological thriller. The approach to the character is working, and Mitchell is chilling (yeah, I went there).
At five episodes in, we still have more questions than answers about the Snow Queen. Questions like: why did she take memories, where did all the other glass in the mirror come from, why does she seem obsessed with Emma? It feels like we should be further along by now.
The Snow Queen, Emma, and Regina took center stage for most of the episode […]
While the Snow Queen plot should be further along, we did see more of how formidable an enemy she is.