Hi Johan,
The short answer is no, it has no impact on performance, and no impact on stability. Indeed this is all completely normal.
You're used to a "simple" form data format,
parm=value&parm=value and so on. Most forms use that approach.
However if a form contains a <input type='file'> then it changes to a different encoding format. This all happens under the hood, and you don't need to worry about it. Both the netTalk client, and server, handle the form data regardless of encoding, and convert it into appropriate "Values" in the value queue.
Cheers
Bruce