I did my last one at On-Track Aviation and really enjoyed it. We had some great group-based presentations/role-plays which were both fun and educational. The more lectury stuff - updates on EASA-FCL etc - was inevitably not so entertaining but it was well-researched and presentations generally good.
Where I work we're usually on our own or with one other instructor so seminars are a good opportunity to meet and talk to other instructors.