Here are some useful links to evaluations:
"Alpha and the New Evangelization," Paul Likoudis
"The Alpha Course: An Evaluation," William J. Cork
The "Alpha for Catholics" website is where you can find the names of all their supporters. In general, it seems to be a very Protestant approach to Christianity with a little Catholicism tacked on at the end.
The aim of the Alpha course seems to be to a "lowest common denominator" version of Christianity, with everyone affirming the absolute basics but leaving out issues like authority, the nature of justification, grace, the sacraments, the Eucharist, priesthood and so on.
We do not recommend the Alpha program for use in Catholic settings. Instead, we recommend the excellent Marian Catechist Apostolate, which was founded by Fr. John Hardon, SJ, and whose spiritual director remains Cdl. Raymond Burke.
Cardinal Burke has warned against using Alpha, and has forbidden any members of the Marian Catechist Apostolate from using its materials because of the danger to the Faith. His email is reproduced below:
TO: All Members of the Marian Catechist Apostolate
FROM: Raymond Leo Cardinal Burke
International Director of the Marian Catechist Apostolate
SUBJECT: Directive to Marian Catechists regarding the program "Alpha in a Catholic Context"
DATE: December 3, 2015
It has come to my attention that a program called "Alpha in a Catholic Context" has been recommended to some Marian Catechists.
Having studied the program, both from the perspective of doctrine and methodology, I must make it clear that the program may not be used, in any form, in the Marian Catechist Apostolate and that Marian Catechists are not to become involved with it.
While, like so many similar programs, Alpha may seem to offer a more attractive and effective form of evangelization and catechesis, it does not have the doctrinal and methodological foundations required for the teaching of the Catholic Faith. Marian Catechists should continue to use the Catechism of the Catholic Church, together with the courses of the Servant of God Father John A. Hardon, S.J., and my "Commentary on the General Directory for Catechesis."
I recall to all Marian Catechists the words of Pope Saint John Paul II in his Apostolic Letter Novo Millennio Ineunte, regarding those who think that, before the challenge of a new evangelization, the Church needs to discover "some magic formula" or invent a "new program": "No, we shall not be saved by a formula but by a Person, and the assurance which he gives us: I am with you."
The saintly Pontiff reminded us that the program by which we are to address effectively the great spiritual challenges of our time is, in the end, Jesus Christ alive for us in the Church. He explained:
The program already exists: It is the plan found in the Gospel and in the living Tradition, it is the same as ever. Ultimately, it has its center in Christ Himself, Who is to be known, loved and imitated, so that in Him we may live the life of the Trinity, and with Him transform history until its fulfillment in the heavenly Jerusalem. This is a program which does not change with shifts of times and cultures, even though it takes account of time and culture for the sake of true dialogue and effective communication. (No. 29)
The Servant of God Father John A. Hardon, S.J., understood profoundly the truth of Pope John Paul II's words and, through the spiritual and doctrinal formation of the Marian Catechist Apostolate, as he so faithfully and wisely developed it, Marian Catechists understand the same truth and are not allured or deceived by stories of a "magic formula" or a "new program." In short, Marian Catechists understand that our program is holiness of life which flows from a profound knowledge and ardent love of Christ Who is alive for us in the Church.