We have used A Baby's Best Friend twice now for a crib, once while staying on property (2009) and once while staying off property (2010). I have to say, I was less impressed the second time around with them.
The first time we used them, the crib seemed almost brand new and the mattress was very firm.
The second time, the crib was more beat up (still clean and safe though) and the mattress was much much softer (again, still clean and in good shape). I wasn't too concerned about the mattress because DD was 15 months old at the time, but if I had a real little one, I might have been more concerned.
Thanks to the poster who stated you have to move all the items yourself when doing a split stay. We are doing a split stay for the first time on our upcoming trip and I was worried that this would be the case.