I can respond to the radiology practices. I think that now with the competitive nature the average amount of vacation time for private practice is about 12 weeks. I have seen practices with 15 weeks or more. It is highly unusual in private practices for partners to get less than 9-10 weeks off. The new hired radiologists before they become partners are usually given about 8 weeks.
I am in academics and it is a little different. I only "officially" get 4.5 weeks but I also get 3weeks conferance time, academic days and certain comp days and holidays; adds up to about 9-10 weeks of "vacation" off the schedule not including weekends. Academic practice generally gives lower amounts vacation time, but at least we make less money!!
A good source to surf if you are curious about vacation time offered etc is <a href="http://www.physicianwork.com" target="_blank">http://www.physicianwork.com</a> There are thousands of jobs in all specialities and most say the amount of vacation time and rough estimate of life-style.