SDHC vs SDXC (1 Viewer)

If purchasing a card now, what would be differences between these two card formats? Are SDXC cards faster, or is it just that sometime in the future they probably will be? and can an existing SDHC reader be used to read a SDXC card?

thanks
Niels

It looks like I answered my own question through some google searches, so will pass this on to see if everybody agree?

1 Many current SDXC cards are not faster than the fastest SDHC cards, but some are
2 Yes you need a new card reader that is prepared for the format.
3 You also need a Win7 PC (I have no idea about Mac) b/c the file format is not supposed to be compatible with my old WinXP?

thanks
Niels

At this point in time then, although Firmware upgrades may allow most newer DSLR's and compacts to use SDXC cards, they offer no real benefit other than larger memory sizes. Great for those shooting endless videos in 1080HD but for a lot less I'd rather buy cheaper SDHC cards. At least if they stop working, replacement cost is going to be a lot lower.
Give it another year or so though and the SDXC standard will probably have increased capacity ever higher, and have possible write read / write speeds far in excess of what our cameras are capable of.