Drupal to Elgg - integration or migration?


I'm getting to grips with Elgg - really like what I've seen so far! Just looking for some advice...

I currently run a popular Drupal site, which is gradually evolving from a content resource  to a networking/community site.

Now Drupal does the content management really well, of course, but the community/group aspects rely on a whole bunch of plugins which don't necessarily integrate very well. I think Elgg might do this better, as a dedicated networking platform.

Migration from Drupal to Elgg seems quite doable - I read some interesting stuff here

But I'm a bit worried about losing all the extra things that Drupal does offer - content management, html newsletters, shopping cart, etc. So perhaps an integration of Elgg+Drupal with a single login...?

The Packt 'Elgg Social Networking' book states that Elgg can be integrated with Drupal, but I've seen no plugin or bridge for this. Now I reckon the author was referring to the OpenAcademic integration project... but that looks pretty dead to me. Seems to have evolved into more of a paid service thingy.

Does anyone have similar experience or comments on this? Anything much appreciated!

Thanks, Jason