I voted "neutral". Because while I adore just Tess (and it's a serious contender for my short list), I'm just meh about the longer Tessa. The "A" seems superfluous--technically, both Tess and Tessa are diminutives, so I really don't get the point of giving a nickname as a full name that will be nicknamed even further? Why not just go for Tess? At least, in my case it feels that way. There's nothing wrong with Tessa--in fact, I used to vastly prefer it to just Tess, which I had negative associations with (that I must have completely left in the past, because I love it now!)--but Tess has more personality and spunk to me, which I love, while the "A" on the end makes Tessa somehow seem a bit wishywashy to me. I do think it's pretty, though, and Nora and Tessa are sweet together.