ABR11 and Lotus Domino

Like all backup tools, it can, but on restore, your Domino server will have to fixup all databases.

AFAIK Acronis doesn't provide an agent for Lotus Domino. So to get really consistent NSF backups you'll need to:

a) switch to a backup solution that provides you with a backup agent for domino. This way you'll also get some additional features (like document restores, point-in-time restore...)
b) stop your domino briefly until acronis started the backup and did the snapshot. You'll face only brief downtime (2-3 minutes on my 2 dominoes) and get consistent backups. Acronis provides script hooks for this.

If you insist on b), but don't want the 2-3 minutes of downtime, I'd suggest looking at clustering your Domino environment.