Personally, I really like the concept of "try before you buy". I think that if I'm supposed to actually pay for software, it would be very nice to see if it meets my demands.
When I was buying my headphones, the shop I bought them at let me test the pair I was interested in, even though they only had them boxed and not on display. The cashier just unpacked them for me and accompanied me to one of the hi-fis in the aisle, put a CD in and let me listen awhile. It was really nice to be able to just listen to music (which, after all, is usually the main purpose of that particular product) and judge whether or not I like the sound, instead of staring at specifications of several models and trying to assess which bunch of numbers will work better for me.
Of course, the evaluation was very short (I listened to two songs) and restricted (I couldn't choose what I'm listening to. They just gave me whatever CD they happened to have at the ready), but it gave me a general idea of what I'm buying. I just think it's a nice option to have.