The pro is you can get your average CD price to be at least half-retail.
The biggest con is just convenience...it isn't something that you go on and just get one CD. You usually need some inkling of planning and research (as you search through titles). Shipping charge isn't so bad, shipping time is probably worse. Which again means that you need to plan and buy things in bulk along as when great deals come by. With music points, referrals, and good deals you will get great price savings.
It isn't something that you want as your only way of buying CD's...but its a great way of buying tons of CD's you missed while saving enough money in doing so to afford buying other CD's normally from elsewhere.
So basically I use BMG when convenience isn't a factor, save money for when I do want to buy any new release on an impulse which I'd probably get gouged on at some retail store or other, so its basically a win win situation if you use it right.
Grrr, when I came back from Europe, they were giving me buy 1, get 2 or 3 free (don't remember exactly) and 1.99 unlimited...yet because I didn't really have a stack of CD's in mind to take advantage of it already has switched to 2/3 off...which although sounds good, with shipping and high normal price it is only a mediocre deal compared to what it was before (which would have definitely averaged to around $4-5 a CD including tax for me).
I have noticed lately that a lot of "original" CD prices have been inching upwards towards 17.98!!! When I first joined the average original price was probably 14. This basically means that the 1.99 unlimited really is a great deal compared to % type savings. A high % off isn't too great if they jack up the price. Why CD prices still are going up when they actually have saved a lot of money using Internet transaction in bulk, when people still can have Mp3 as a cheap alternative, or forthcoming new media formats, etc., is something to wonder about from record companies.