Personally, as a buyer I don't care a hoot about whether the item is marked "eBay Plus" or not, it makes no difference to me at all, I never notice or look for this.  If I want to buy something I do.

As a Seller, I don't offer free postage and don't want returns, I think that any buyer who goes out of their way to choose Ebay Plus, may be just the very ones I would like to avoid....eg..the ones who expect everything for free, and if they don't like the product or change their mind, expect the Seller to pay to get it back, which I believe can be up to 30 days later, (after they have used your item, damaged your item or whatever)  The rule to have to offer no extra postage on additional items, leaves me speechless, so the seller should be out of pocket for this? I don't believe any of these schemes set up by eBay are any benefit to Sellers, but that is just my opinion.

Take the one "guaranteed delivery in 4 days"  and  "guaranteed posting in one day"  I coudn't even contemplate those without a very good and reliable crystal ball.  The only thing "quick" that I can see, is a quick way to get into trouble with eBay for failing to deliver on these.