I recently wrote a review for the feeldoe which addresses some of these issues... You can read it HERE
(It is also in the rumble this week. We loved the feeldoe, but wished we had purchased a different model than we did. I have also used the Share, which is similar to the feeldoe.
The biggest problem with the feeldoe and share is that they might not stay in as easily as you want it to. However, use them in conjunction with a harness and your support is taken care of and you are "connected" with your partner as it is one toy inside both of you.... which is definately a great feeling.
As for which harness, I have only had experience with one, but it has been widely acclaimed as a great harness, the SpareParts Joque harness. I also reviewed that one, and can be read HERE
I still like the harness with other toys better than the Feeldoe/share, but they are different sensations, so I am bias due to that.....