OK, I installed my fan. First I left the switch I installed off so when the damper opened the fan did not run. Worked Ok but I felt that it took too long to come up to temp due to much less natural air flow. So, I modified the fan housing to let more air in. I also made a cover so when I turn the fan on, it works as designed. With the fan operating, I agree that my boiler recovers much faster. Haven't noticed needing more wood, but haven't run it long enough to know. I purposely put in a load of "wet" wood with some very large pieces that I had to roll in from my skid steer as a test for the fan. Stuff burned great with no problem. The smoke seems to be the same while burning but shorter burn cycles makes for less smoke in the end. I did notice that my water temp goes a few degrees higher after it shuts off than it does with no fan. Not really a problem unless you are set at a high shut down temp. I think it will help out a lot when I get back to heating my pool.
I think having this fan and the option to use it when I want will just make a good boiler better.
Here's some pics, the holes you see in the fan housing I put there for more natural draft. They are NOT there originally.