I saw a note flash up while on Ebay today, saying that Ebay and Paypal are separating (divesting), so I looked it up to see if it will change anything.

As far as I can tell it shouldn't change anything for us regular users... at least in the short term, but check out their User Agreements if you are a heavy seller/buyer on Ebay.
However, if they are now going to be separately listed companies on the stock-exchange and eventually gain separate owners through share-trading, they might end up removing the interlinking ties like the "one login for purchase and payment" feature that they instigated a year or so ago, or any pre-filled payment forms/boxes, or specific paypal guarantees for Ebay purchases... so I thought it was worth mentioning this just in case there are some significant changes soon, or later (the divesting is to be completed by mid-June).

For them, the separation is purely money motivated (like anything with big corporations). It seems that merging to become one of the biggest companies in the world limited the amount of money they could earn from partners and advertisers, who are only dealing with a single entity after the merge... so being separate companies, they get double exposure to their partners and advertisers, and their money.