There should be no problems - when you buy a book, it'll get downloaded to "My Documents\My Books\eBook Library\", from which you can just import it into Calibre & use Calibre to communicate with the Sony. The LRX books will have 'odd' names, but Calibre can read their titles & authors from the metadata. (Interestingly, the Google epub books have reasonable names.
You can also just export the books you want from Calibre to a folder, then use the Sony software to copy them to the device - you'd gain the pre-formatting, but loose the automated categories that Calibre provides.
You could even use both, although I'd suggest that just to be safe, you only run one at a time!
Being in the UK, I can't register a CCard to buy books from the Sony store, but I have bought some with voucher codes & occasionally grab their freebies, all of which are DRM'd LRX - the bulk of the books I read are LRF though & while I did used to use the Sony software, I've switched to Calibre & have used that for over the last couple of months.
[More...] My experience differ's from kiklop74's! The Calibre issue refer'd to is almost entirely with News content (i.e. it might be possible to create books that show it, but normal one's don't) - also, if applicable, you'd have already hit it! I think you'll find many Calibre users don't use the Sony software at all & there's NO problem in using it for transferring LRF files in general.
Last edited by gwynevans; 03-19-2009 at 08:27 AM.