Sure I do. I use it to kill the exchange email sync, because it triples battery usage even when I have it set to not sync (I believe this has something to do with the fact that it's just scraping Outlook Web Access, not actually connecting with Exchange, which is impossible outside of the firewall.)
And I use it for this sort of thing frequently. Most services pull down battery life considerably.
With these services up, my Droid loses maybe 40% of its battery life in a day (with minimal usage.)
While I sleep, it rarely consumes more than 10%. The counterexamples have been when I've left the Pandora Service running, as well as the Email Sync service.
So, I test it by enabling the service, changing nothing else about my usage, and watching my battery life take a nosedive.
And on the subject of what exactly it's doing, that's roughly the explanation I got from my friends on the Windows side. We have Exchange disabled outside the firewall, so my phone has to hit up OWA to get the data. Is Exchange Web Services an API available from OWA, but separate from the HTML? It's my understanding that my phone is in fact scraping the HTML.
There's 4 different interfaces that use the same OWA URL but function completely differently. There's the web based email that people typically think of when someone says "OWA". There's WebDAV, which uses HTTP or form based authentication (to pick up the proper cookies) and then uses special URLs and WebDAV HTTP verbs to perform actions relative to retrieving/sending mail, listings, calendar, etc (this is in the process of being deprecated I believe). There's Web Services, which is (if I remember correctly) a SOAP API that provides the same functionality as WebDAV (and some additional functionality) which has become the preferred method as of Exchange 2007. There's ActiveSync, which uses WBXML formatted message passing (it's more complicated, but more robust than WebDAV and Web Services). If you're using k9mail to talk to an Exchange server, it uses WebDAV. If you're using the "Work Email" app, it will use ActiveSync, Web Services and WebDAV, depending on which is enabled. If you're using TouchDown, it will use whichever of the three you select.
Frequently in configurations, WebDAV access, Web Services access and ActiveSync are all enabled when OWA is enabled for the Exchange server. It is only in rare conditions when you will see OWA enabled and not one of the three.
And I use it for this sort of thing frequently. Most services pull down battery life considerably.