Lesa, they are slightly softer and milder after being frozen. Turnips can be used just like a potato. They can get a little sharp (think mild radish) if they get too big, or the weather is dry. My favorite way of making them is:
2-3 turnips
1/4 lb (maybe a little less) mild italian sweet sausage,
fresh herbs from the garden...thyme, oregano, rosemary...to taste
1 clove crushed garlic
Slice the turnips as you would potatoes for frying.
Brown the sausage and garlic.
Add turnips and herbs
Fry over low heat until the turnips are light brown (just a few minutes).
You can also add them to mashed potatoes to give the potaotes a flavor boost. To me mashed potatoes are kind of bland.