Well, I just finished a Steel monotype challenge on Platinum... Even though I didn't actually make any posts here, so it didn't actually count. Eheh. Oh well, it was fun anyway.
I beat the Elite Four with Empoleon, Bronzong, Scizor, Magnezone, Steelix, and my HM slave Lucario (who was only good for switching in and getting KOed while I used Revive on someone else). Post Elite Four, Lucario was briefly replaced with Dialga, who's now been replaced with Skarmory.
For anyone else who wants to try a Steel run: Levitate and Magnet Rise are your best friends, because everyone uses Earthquake. You will also learn to loathe Cynthia's Garchomp and Flint's whole team.
Well, that was fun. And I have new sympathy for all those poor gym leaders that can be blow away by a single Pokémon with a single type-advantage move.