I rented the 105mm f/2.8 for this week (has to go back this Friday). I have only taken a few shots with it so far, but I can tell you that it will be my next lens. It is a bit pricey, in fact, even the used and refurbished ones are only a slight price break. At close to $1k USD new, I'll have to save for a bit to get this one. It will round out my very modest collection of lenses. I didn't know what I was missing until I rented this lens, and I am anxious to do more with it.
Not having tried the 85mm, I most definitely fall into the biased crowd in regards to this lens. As others have stated, it will come down to what YOU think and want to spend. (Value being an individually relative term). Is it worth it to YOU? But if you are undecided, maybe try renting the 105mm and comparing it to the 85mm before dropping any money on purchasing either. One of the many benefits of rental lenses is the "test drive" factor, allowing you to try before you buy. That way, you can make a more confident purchase and know that what you purchase is what you want and will make you happy.