Just to second Tamerlane - Mohammed’s restrictions are seen as very progressive and pro-women, as previously a man could marry as many women as he wanted, and not have look after their economic wellbeing or anything.
From talking to Muslim colleagues and other Muslims here, it seems that the practice of multiple wives is definitely on the wane. There is even some disapproval of it in certain quarters. That said, very, very rich and important men such as sheikhs may have multiple wives. This is often for political reasons - such as to align with more than one other important family, or to increase the chances of male heirs etc.
But from talking to more man-on-the-street Muslims, it may be mentioned that “an uncle” or “a grandfather” had two wives, but it never seems to be a brother or a cousin, which has led me to understand that it is a practice that is reducing over the generations.
I have also noticed that divorce does not seem to carry the same stigma here that it carried until quite recently in Western/christian society, especially for women. This is probably because the Quaran makes provision for it, so you don’t have the “can’t marry again in church” thing that we still get today, or the phenomenon of having to “catch your partner in the act” before no-fault divorces came out. When a man divorces his wife in Islam he is required to make provision for her and her children. It’s also a common practice for a man to settle money on his wife so she is economically independent.