What problems, if any, do Biblical Unitarians have with the Apostles' Creed?

• We believe in God, the Father almighty, creator of heaven and earth.
• We believe in Jesus Christ, his only Son, our Lord.
• He was conceived by the power of the Holy Spirit and born of the Virgin Mary.
• He suffered under Pontius Pilate, was crucified, died, and was buried.
• He descended to the dead.
• On the third day he rose again.
• He ascended into heaven, and is seated at the right hand of the Father.
• He will come again to judge the living and the dead.
• We believe in the Holy Spirit,
• The holy Catholic Church, the communion of saints, the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.

Quotes from linked pages noted below.

The Apostles’ Creed, in its early form believed to date back to shortly after the time of the apostles themselves, does not mention the Trinity or the dual-nature of Christ.

It seems that if the doctrine of the Trinity was genuine and central to Christian belief, and especially if belief in it was necessary for salvation as many Trinitarians teach, it would have been clearly stated in the Bible and in the earliest Christian creeds.

There are some ambiguous terms that may provoke resistance.

• his only Son - Obviously there are many 'sons of God', but none holy as was Jesus, being without sin.
• He descended to the dead. This may look to 1Pet 3:18-19

put to death indeed in the flesh, but having been made alive in the spirit, 19in which also having gone, he preached to the spirits in prison...

If it means Jesus went to 'hell' or some other description of the under places, then there is a problem as the text doesn't state this because he was still dead and not doing anything while in the tomb. Only once he was raised, "made alive in the spirit", did he preach... If he died "in the flesh", then he was dead until he wasn't - which is his resurrection to new spirit life.

• seated at the right hand of the Father. This is not stated anywhere, but is at the 'right hand of God'. 1Pet 3:22, Acts 5:31, Luke 22:69, Rom 8:34 and numerous others.

Reference to a Biblical Unitarian page on the various creeds.

Dale Tuggy, a Biblical Unitarian, discusses the Apostles' Creed in this podcast. He says

"The creed has been called 'Trinitarian', in that it starts with the Father, then moves on to the Son, then finally to the Holy Spirit. But it doesn't so much as hint that these three are one God, or say that they are equally divine persons within one God. The creed presupposes monotheism and it two times tells us who the one God is. It is the Father Almighty. It presupposes, then, that the one God is not the three of them put together, as Trinitarian theories have it. We also don't see here what is nowadays called the doctrine of the deity of Christ, we don't see the claim that Christ has two natures - a human nature and a divine nature. Nor does it mention Christ's eternal generation from the Father or even his existence before his human life. The Holy Spirit just gets a brief mention. The Holy Spirit is not asserted to be personal or to be a divine person equal to the Father and the Son, nor is the Spirit's eternal generation from the Father and the Son mentioned. The reason the creed doesn't mention these things is that when the creed was first written - or perhaps when its ancestor documents were first written - these things were not widely taught."

So vis a vis Trinitarianism, this creed does not seem to present a problem for a Biblical Unitarian, despite a so-called 'Trinitarian structure', whatever that means exactly.

However, Tuggy does go on to raise concern about the phrase "descended to the dead", suggesting it is based on a slight scriptural basis and perhaps misleading (see @SteveOwen's answer), and the phrase "The holy catholic church" which, he claims, in its original sense might have been churches with Bishops, and nowadays would be limited to certain churches derived from those, although Protestants often interpret this phrase as meaning the body of Christ - i.e., all Christians that form a universal 'church'.

So, I think the answer is that the creed is fine for Biblical Unitarians, as much as it is for Protestants in general, i.e., some might have reservations about a couple points, but these aren't dependent on Trinitarian considerations in particular.