Michael Poterman, who isn't Catholic, calls it a "marvelous form of contemplative prayer" in the latest dead tree National Review:
[This is a] specifically Catholic form of devotion that deserves a lot more attention from other branches of the Christian community...Owing to the repeated prayers, it has been viewed with great suspicion by Protestants anxious to avoid the “vain repetitions” Jesus warned against (Matt. 6:7). But the repetitions are actually a great aid to contemplation: “Changing the rhythm of one’s life, freeing the mind to move in a different way, involves slowing down the tempo of thought, entering a stalled state.” The idea is not to wear out the divine Hearer with a rote recitation, but to calm the mind of the one who is praying — and thus enable him to focus on the Bible scenes being meditated upon. I would add another consideration: The chief impediment to prayer is distraction, and the rosary helps solve this problem by building the distraction into the prayer itself. If the mind wanders from the mysteries, it can wander to the repeated prayers — and vice versa. To wander away from the prayer entirely requires more than the usual amount of mental agility.
Another objection frequently raised to the rosary is that the prayer most frequently repeated within it is addressed not to God, but to Mary. Is this not idolatrous on its face? Wills ably explains that this asking for Mary’s help is not idolatrous; it is, he writes, merely “to rely on our fellow member of the mystical body of Christ.” It is standard practice among Evangelicals to ask our fellow church members to pray for us; the Hail Mary simply extends this practice to the woman who was the Church’s first member. (Anyone whose theological conscience absolutely forbids addressing in prayer — of any kind — a non-Divine person can replace the Hail Mary with another short prayer, e.g., “Lord Jesus Christ, Son of the Living God, have mercy on me, a sinner.” What’s essential for this form of devotion is to preserve its two-track structure.)
In 2002, Pope John Paul II expressed the hope that the rosary could become “an aid and . . . not a hindrance to ecumenism.”