All 4 of our tires are foam filled on our TC40D (they were when we purchased the tractor)...
The good...
- no worries on what we drive over in the woods (or anywhere else)
- the weight (it works for us)
The not so good....
- ride quality (especially on hard surfaces) we are almost never on hard surfaces like asphalt, roads , or concrete so it is ok.... just ok....
- Ice... not good... I chain all 4
- Tires have zero give so traction can some times be an issue.... but with 4 wheel drive not usually...
- the weight.... if you need to remove them.... we have a tire dolly (oh & a Lull) so not a really issue.... but something to consider