I have played in and ran very high level games. They do work, but require extra attention by the GM, particularly with creative spell use.
One of the unadvoidable balances in the game is just how tough Super Large creatures are. You can be 8th level or 80th, a SL foe is HARD to kill, and will get several oportunities to inflict pain, suffering and death on PC's. SL foes with minion is the worse, as it prevents PC's from trying to absorb the brunt of the SL foes attacks while the others hammer on it. Even a fairly low OB SL foe can do considerable harm, including kill, high level PC's.
I had a party of six high level PC's, Thulsa (level 80 something fighter with sorcerer base list and some closed ess), Arden-Tul (close to 90th level rogue Wose with considerable tech items, including a barrier shield from SM2), Tensen (mid level 60 warrior monk who weilded the power of justice), Alashieve (level 90+ fighter with a freaking list of artifacts), Solon (level 51 fighter northman), Will (level 48 or so healer) and Fee (level 100 mage/archmage). All but Fee died in four melee rounds of combat with 16 Major Wights (Fee was not present, and the party engaged in a head on assualt). They could fight the wights and seriously out matched them in OB/DB, but they had no way to counter the 30' radius C cold crits every round. The last to fall was Alashieve on the fouth melee round, and I will never forget the hushed silence at that table. Four years of gaming several days a week with many marathon 11am till 6am the next day sessions, and it was over. If those foes had not been SL, that party would have crushed the wights and fast, maybe two rounds at most.Â
Personally, I was glad. We had a great run, and I was a bit tired of coming up with new challenges for such a group (a group that faced and lost to the Witch King and his minions, then beat him in the rematch, defeated TWO Black Reavers in a single combat, though I dropped three of em in the fight and sorely hurt the other three, including dropping the mage in one single blow, and even had the moxie to try to bum rush Sauron, who captured them all with one spell and had them cast in a dungeon, then possessed and used as slaves before they were freed via Fee regaining control of himself via a will contest with his demon, then having to fight the said demons once they were "pulled" from their bodies, but not before they wrought awesome damage on Lothlorien and before that, Pelagir in Gondor).
That game covered almost a century of in-game time, time travel (twice), a visit to the Undying Lands, crushing the reformed Sauron in the future after it was discovered the crack of doom was a gate and did not destroy the One Ring, travel to the Shadow World (which was a brand new release at the time)...I mean, I worked my butt off on keeping an interesting and challenging story line, something that is much easier with level 1-25th level characters.
lynn