I picked up one of the new 32gb Sandisk cards from Verizon for $75 this week. I thought I would post up a speed comparison since many people seem concerned that it's only a class 2 card. I performed a full format on the cards (except the brand new 32gb which I quick formatted) to make sure they didn't have any data on them prior to testing them with Crystal Disk Mark.
The net of it is that the 32gb class 2 card is either almost as fast or significantly faster (depending on the test) than the 16gb class 4.
It seems to be exceptional at doing non-sequential writes in particular. I actually ran it several times just to be sure it wasn't some kind of fluke. All of the cards performed well beyond their stated class (especially the class 2 cards). Any of these cards are more than capable of keeping up with anything that the Droid X (or any other smartphone) can throw at it.
For reference purposes, the Droid X records 720p at around 23 mbps or less than 3 MB/s per boygeniusreport.com.
EDIT: I took a few videos myself the other day at 720p, and my videos all came in at just under 1 MB/s. I'm not sure what explains the difference between my own files and boygenius, but either way, they're both well under the capabilities of any of these cards.
16GB Class 4 (came with the Droid X)
Sandisk 16GB Class 2 (bought it of off 1saleaday.com a month or so ago)
Sandisk 32GB Class 2