Other Flarm users. If you are in Stealth you give no more warnings to other users than you receive. So non-stealth gliders will not see any more than your fellow competitors.

This has the unfortunate effect of causing gaggles to 'appear' with very little prior warning.

So... a fast moving powered aircraft that happens to have Flarm will have seconds worth of warning that you are about to collide which may not be sufficient. I'd be concerned about the liability issues if this was to happen because you had degraded your collision avoidance systems - especially in the US!