As the catcher or receiver? Lol!
Years ago I tried it out with a lady dom. She said that she liked having the cock inside her without the straps, but there are some definite limitations to it. One thing is that its not really phallic in shape, so if you want to do oral submission, the bottom won't get as good a feeling as sucking a cock.
Now the exact shape is not so important for anal play. Penetration is penetration, and size DOES matter!!!
lol! But from what my lady friends have told me, while its fun to have a strap-free expereience, you can't really use the feeldoe like you would a really well-fitted strapon harness. Your vaginal muscles simply aren't up to the task of holding it that strongly, and when you add some juices into the equation, well, it becomes nigh impossible!
So don't throw out your strapon harness just yet. It still has it uses. But do get yourself a feeldoe and have some fun.
Remember, when the going gets weird, the weird turn pro!