I think it is definitely a positive reflection of love and marriage. One of the aims of the play is to show how love is perfectly suited for marriage, so this is why all of the couples end up happily married in the end. Despite the troubles the couples go through, they end up happy in the end. As Lysander says near the beginning of the play, "The course of true love never did run smooth."
Whether or not the play is considered a criticism or a celebration depends a little on one's viewpoint. At the beginning of the play, in Act 1, sc. 1, Theseus is anxious for the upcoming wedding and Hippolyta seems a bit reserved, probably due to the fact that Theseus "won" her by defeating her, but Theseus tells her that despite how he got her, he looks forward to marrying her. The relationship between these two characters is certainly odd because of how they came to be together. The relationship between Helena and Demetrius is rather odd, too, because it only came about because Demetrius was annointed with the magic love-potion flower Oberon had Puck find so he, Oberon, could use it on Titania. The love Demetrius feels for Helena isn't "real". The relationship between Lysander and Hermia seems to be the most sound relationship because it only changed when Puck accidentally annointed Lysander when he was supposed to annoint Demetrius. Even the relationship between Oberon and Titania isn't without problems. While it seems that there is a great deal of manipulation to get people happy with their relationships in the play, by the end, all the couples are happy. So, while some might look at the play and see all the manipulations and trickery suggest a condemnation of love and marriage, others might say the happiness at the end is a celebration of love and marriage.