USA Baby mattress/squared corners?

Hi - We found what we think is a great mattress @ USA Baby, but it's a bit pricey and we are not certain if the features are truly good or just gimmicks. 1.) It is very firm foam on one side and coil on the other. The idea is to be able to flip the mattress and use it as baby gets older. 2.) It also touts squared corners -- which the sales associate says is much better than rounded corners. However, we see no other mattresses with squared corners... 3.) And the mattress can come upgraded with a vibrator. What is your input on all of these features? The mattress is fairly new so there is no info in the bargains book. Thank you!

We just bought one of these this weekend. We got $10 off, since we bought the crib at USA Baby as well. I wanted to go with either of the top 2 models, since they were waterproof and had the foam and coil on each side. I think the waterproof aspect is totally worth it, instead of having to pull off a waterproof mattress pad all the time. My husband liked the vibrating one, so I agreed. I think it was about $50 more than the other non-vibrating one and we figured if the baby is really cranky one night, we tried everything we could think of, and the vibrating matress made her stop crying, that it would be worth the $50 for some sleep. :-)