Visitor Stitching Should Not Split a Visit
SC15 introduced an awesome new feature, visitor stitching. However, when this is used (setting s.visitorID), it will split the visit when a returning visitor logs in on another device. If they then return on that same device I think it's working fine, but that initial login is splitting the visit. This is a big deal and is incorrectly counting visits. I can try create some calculated metric, but it would be complex and I can almost guarantee the numbers wouldn't be accurate.
What should happen is when the visitor first logs in on a new device, and s.visitorID gets set with a new value, it should preserve the visit. That way pathing and visit numbers would not break mid-visit, and the visitor stitching solution would reach its maximum potential in value. Until then, it's a nice feature but this one aspect of it is very unattractive.
Here was how I found this out. Another company first reported this to me after I helped implement it. I created a new report suite, had visitor stitching turned on by Client Care, and then did some testing where I sent data normally without setting s.visitorID. While that visit was still active, I set a value for s.visitorID. I waited a day or so, looked at the data, and was able to see that there was a count of 1 visitor and 2 visits.