Thought I'd post this for anyone who's looking at SDXC cards and finding as much confusing information out there as I am. I recently ordered a 128gb SDXC card to use for video on my Canon T2i camera.
Looked around on the internet and on this site to try to determine if the card would also work with my W510. Pretty much everything I found online indicated that the card reader on the W510 probably would not work with the exFAT file system required for SDXC. Even the support site at SanDisk contradicted itself. In one place it indicated that an SDXC card could be used in an SDHC reader as long as the operating system supported the exFAT system. Windows 7 supports the exFAT system natively. Then further down on the page it indicated that SDXC cards could only be used in SDXC devices.
Another site I found indicated that the Ricoh 5-in-1 reader included with the W510 would work with the SDXC card but not with the exFAT file system and therefore might have trouble with any card over 32gb. Their resolution was to change the file system... which would basically mean the card would no longer truly be SDXC.
So, I didn't find anything conclusive. I got the card and of course the camera supports SDXC and all works well there. Decided to try it in the W510 and was very pleasantly surprised to find that it worked. Clicked on properties it indicates the file system is exFAT and recognizes the full capacity of the card. Was able to open photos and videos from the card using the card reader that came in my W510.