Consider: what does a swapfile do? Provides extra space for the OS to use when real memory runs out. What does a RAMdisk do? Takes away real memory to create a virtual drive. So you then set the swapfile to appear in the RAMdisk. Now, Windows has less real memory than it started with, and uses another part of real memory to store the swapfile which is supposed to store the data that can't fit in real memory.
Granted Windows does sometimes use the swapfile for no reason, but using a RAMdisk to store the swapfile is counterproductive. You'd have to increase the total amount of system memory, in order to allow Windows to have the same amount of memory available as before, while also having memory for the RAMdisk. That can get expensive quickly.
What a RAMdisk can be used for is storage of specific data that you need quick access to. You have no control over what Windows puts into the swapfile. But perhaps you have a large database which always benefits from faster access. Putting it into a RAMdisk allows extremely fast access. But for most databases that need such speeds, it's going to be a very large database, requiring large amounts of memory, which would cost a ton. Even a RAID array with the fastest SCSI drives becomes a cheaper option at some point, and still provides good performance. Of course, for servers, they're already going to be getting lots of memory, but then you still have to increase the total memory to accomodate both the system memory and that for the RAMdisk, AND they're probably also already going to be running a RAID storage system.
A RAMdisk could also be used to increase performance in games. Installing a large game directly to a RAMdisk could result in faster loading times for maps and textures. But again, it gets expensive to have enough RAM both for storing the files in the RAMdisk as well as having enough memory for the OS itself to use. Plus, the swapfile might still be a limitation, especially in the initial loading of a game when the OS is clearing other applications to the swapfile. So now you maybe want to include the swapfile in the RAMdisk, which means even more memory needed.
Figure that some games these days are taking up over 1GB of drive space, and some barely get adequate performance with 512MB of memory, and now you're up to 1.5GB to 2GB of system memory. If by chance you had 4 slots for PC2100 modules, that'd cost you nearly 300 dollars from Crucial. More likely you only have 3 slots, or only two if you want to run dual-channel memory, and now you're talking about 1GB modules at almost 600 dollars apiece. An IDE RAID array would provide good performance and cost a quarter of what 2 gigabyte modules would.
That's also only to have ONE game installed! You'd either have to have even more memory for the RAMdisk, or you'd have to move games in and out of it whenever you wanted to play something different.
I'm not sure also about performance of a RAMdisk that's being constantly mirrored to a drive partition. The drive mirror certainly can't keep up with the rate of changes to the RAMdisk, so I'd wonder how far behind it can get if your RAMdisk's files are constantly being changed. If it was way behind and the server crashed, you wouldn't have the most up to date versions of the files. It'd be like a write cache in Windows, but an order of magnitude worse. Reading the features of the SuperSpeed software, it looks like writing to the RAMdisk can be slowed down so that the hard drive can keep up, while reads are allowed at full speed. Kind of kills the benefits of using a RAMdisk, but at least you have the option.
Oh man, I just got to the part about "SuperCache", which allows you to put only part of a partition into actual memory, while the rest is maintained on disk. Then the software is used to dynamically move data in and out of the RAMdisk when needed. So basically, they have a "swap file" software running for an entire partition, taking up space in main memory, so that Windows runs out of main memory and has to use its own swapfile for that data as well. I can only imagine the amount of disk thrashing that would cause.
They only support up to 64GB of memory too. Now, granted not a lot of servers may use that much, but how many people that need such high performance are only making 64GB partitions? Or actually less, since you can only make the RAMdisk a certain size, so that Windows still has some memory to work with.
It seems like a big gimmick, lots of touting of the "benefits" of a RAMdisk without explanation of actual limitations and uses. Sort of like "memory doubling" software from several years ago.
I doubt you'd really see enough of a difference with a separate drive for the swapfiles to make it worth buying things just to do that. If you're going to put in a controller card, put your main hard drives on that card in a RAID array, and the other hard drive on the integrated motherboard port. If you're not ready for RAID yet, don't bother.
if my setup is less than optimal or unnecessary please be honest with me and if you feeling kind please toss me some suggestions. 
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