I had a 5sfe in a '95 camry that was loaded with hard coal-like burnt on "sludge" built up on everything under the valve cover. It was a neglected engine, with a stuck pcv valve non-working thermostat, bad radiator, broken oil pressure sender, etc. It ran like a top up until it had some sort of catastrophic mechanical engine failure.
I think that these are good engines and if they have regular (3-5k mi.) oil changes they are fine. It is pretty easy to pull the valve cover and see for yourself if you have any sludge under there. Plus the valve cover gasket is a common source of leaks in these engines and may need replacing anyway.