I'm in a 24' White Mountain Yurt in the lakes region of NH - with the winter package and an insulated platform about 3' off the ground. The past 3 winters I've enclosed the platform with a ring of bagged leaves and brown tarp. Probably kept it a bit warmer, but the mice were a battle all winter. This year I left the platform open and no mice. Yay!
For heat, I have a small wood stove - a Vogelzang TR-001. I could probably use a bigger stove on some bitter nights, but like being able to keep it burning hot (less creosote build up) for more of the season. Also because I live here, I'm not trying to thaw a yurt frozen solid because it's unheated all week. One might need a bigger stove for that.
Each fall when it gets cold and windy, I go around the inside of the yurt and look for drafts and plug those. That makes a big difference. Rugs on the floor help too, as Jay Aimes said. I personally make generous use of hot water bottles - to heat the bed at night and again in the morning while having tea and checking email - waiting for the stove to get going. Basically anytime I'm sitting still and need more warmth, I use a hot water bottle.
Built pegs to hang things over by the stove like boots and winter gear - both to dry, if wet, or just to keep warm. (Being super careful they will not fall on the stove!). Would love to have radiant heat, but off-grid, so slippers are a must. Also warm clothes as needed. Yurts do get super toasty, but - at least for me - huge temperature variations most days. Because they are tents, right Bob?