Well, writing the forms in partial views creates no issues at all. Instead it facilitates you to develop with ease. If you have used any Scaffolding Library, you must have seen they do implement this practice very often.
A very simple example:
For Creating a record and Editing a record, both will have the same controls on the form - just with few ReadOnly of them. So, here, creating a partial form "_CreateOrEdit" will save your time and efforts.
Just make sure that you exclude tags, I mean @Html.BeginForm() or whatever helper class you're using to generate form tags, in view, not in partial. Keep only the common controls in both.
Hope I'm making sense, thanks!