Educational Technology - Does using a "new" tool enhance learning?

We've implemented several new forms of Educational Technology in the Medical Curriculum at Tulane over the past 6 years, starting with:

• Audio podcasts
• Tegrity classroom recording (where audio & projected video are recorded together & posted online)
• Audience response systems - clickers & histograms (Turningpoint)
• Just-in-Time-Teaching & Peer Instruction
• Team-Based-Learning (TBL)
• Interactive web-based quizzes for self assessment
• Wikis (to replace a text)
• Human Patient simulation (METI) exercises

So far the only methods that seem to make a significant impact on exam performance from our experience are TBL & adding Human Patient Simulation exercises - and only by a few percentage points. It makes me believe that changing the approach to teaching (employing more active learning) makes only a small impact in our realm of education. Is this because we emphasize "memorization" (knowledge recall) too much in the medical curriculum, and one can only improve memorization to a limited extent? Active learning has made huge increases in learning in undergraduate physics - but physics is focused much more on "concepts" - a sharp contrast to the current medical curriculum. Perhaps if the USMLE Step 1 exam were to become more focused on the understanding & application of concepts, this would change?