Well, it's a one-time investment so your marketers/whoever else can make easy changes in the future. Will be useful for SEOs. Personally though I'm concerned by how checking a remote server will add to page load time.

It's a fair concern - we recommend using just Google Tag Manager (synchronous and lightweight) code to fire all your other tags asynchronously. So in most cases, where you call more than one remote code snippet, it could speed it up.

If the request is async, it shouldn't cause any problems.