I've used it in the past with NO harmful experiences. I usually spray for about one to two seconds, thats all it takes. NEVER use it to keep a engine running though. To see why, just spray it into your lawnmower while its running. Knock, knock, knockity.
Occasional ether use will not harm your engine. Ether has gotten a bad rap for many reasons but its rap is mainly form use in diesel engines where it can cause glow plugs to swell (can't remove them) and shooting a flammable fluid into a diesel engine (which has no throttle body) can cause a runaway engine.
Try to buy a starting fluid that contains an "upper cylinder lubricant". Pure ether doesn't have any lubricating qualities and can wash away any oil film in your engine's internals.
PS Be careful, a stray spark or flame when spraying this stuff can cause an interesting fireball. I use ether to start my snowblower and had an interesting mini-explosion from a carb backfire. It was loud and almost cost me my eyebrows.
PSS The use of ether is indicative of a problem with your engine and you should have the affected system checked and repaired.
I've done it on occasion after my '88 NA SE sat for 6 months with no fuel in the tank & a dead battery. Make sure U have fuel in the tank & use sparingly. I have found it doesn't help with a flooded engine. Install a fuel pump cutoff switch if U are flooding out.