Gents,
We're all getting sidelined by physics:
Actually, everyone has a good point, but non yet have covered the 'common ground' Inertia.......
In the hover case, change in direction does indeed change your IAS, as the wind is unable to instantaeously speed you up.... ie headwind becomes tailwind.
In the 'Flying Case', all respondents are correct, but by different levels! In a FJ, it means nothing, in a Tucano it might be apparent in the finals turn, based on your gournd track (as stated). Helos and Hover Jets, I'm less sure, but the point is, that the 'Air' cannot move you straight away, and so there is a 'Relative' change in air motion over your craft. This you see as 'Sheer' or (If you are using a ground reference) IAS loss.
Basically. The 'AIR' has a momentum too, Oh and it's a lot bigger than yours!
Personally, I've only had a scary once with wind sheer, in the Falklands, and that was covered by the 10Kts I always held for 'Granny', Now I know why I did that.
Advo