I think Mirrodin is the second worst block in Magic's history (next to Urza's block) solely because of the monumental failure of the R&D developers.
Design-wise the set is beautiful. The 5 different mana myrs and the 5 artifact lands form a wonderful base to immerse your decks in an artificial plane. Manabases are better than ever because of easy to cast artifact cards and things like the Spellbombs. All the colors have a theme with artifacts.
Artifacts themselves became a color. If you play lots of artifacts, cards like Myr Enforcer, Frogmite, and Lodestone Myr are very powerful. If you supplemented blue, you have Thoughtcast, Broodstar, and Somber Hoverguard. If you supplement black, you have Nims and Skeleton Shard.
Equipment is a flavorful, tournament-worthy revamp of creature enchantments. The vulnerability and awkwardness of creature enchantments made them absolutely terrible for tournament play. Equipment is far more robust.
Imprint is entirely new. The modularity of Mirrodin is unprecedented.
But a great design team and a great creative team can be shot down by the developers. Now for the cons.
For multiplayer, all my opponents simply loaded up on the artifact removal to own me. I can't use Soul Foundry because it gets eaten by Shattering Pulse or Molder Slug. In fact, I can't use expensive or "clunky" artifacts period because there are Pernicious Deeds and Vengeances flying everywhere.
The colored artifacts lands are among the worst lands for multiplayer. One Deed, Vengeance, or Shatterstorm and you scoop. I've lost 12 permanents playing my Myr deck; Vengeance is basically a Jokulhaups targeting me.
What I'm saying is that I couldn't have any fun with my new Mirrodin cards because the answers were far more
brutal than the threats.
One-way untargetability like Troll Ascetic is just stupid. While it feels good when you're on the right side of the table, it's just far too annoying and discourages player interaction.
Darksteel artifacts are even worse. Making threats that are immune to removal is just stupid. This mechanic is should have been limited to Darksteel Citadel, Pendant, and Ingot, since I don't mind robust manabases. Darksteel Colossus is the best fattie ever printed, and he's not green.
Sundering Titan is no fun. At all. Remember when creatures that blow up lands where Demonic Hordes, Seismic Mage, Army Ants? Then they made them better and symmetrical with Keldon Firebombers and Desolation Angel? Well, lots of times Sundering Titan is an 8 mana 7/10 guy that Armageddons your opponent. Should never have been printed.
Skullclamp. Oh Skullclamp. Most tournament-dominating card ever? Top 8's showed up with 32 Skullclamps for 100% of the possible slots. Banned in almost all formats. "Distorting" the metagame is putting it lightly.
Now it seems that Standard, Mirrodin Block, and even Extended are overrun with the strongest and most robust aggro deck ever seen. Ravager Affinity is a deck where half it's plays are free and 1-for-1 artifact removal only loses you tempo if you paid more than 1 mana.
When I go to tournaments, I play Ravager Affinity or I play a worse deck.
I've had fun with Mirrodin cards. I had tons of fun with Skeleton Shard. I have a Power Conduit + Chalice of the Void deck. I have Nightmare Lashes in my Dancing Gnomes deck. I have an Arcane Isochron Scepter deck. I have a Cog / Door to Nothingness deck. I have a Mesmeric Orb deck.
But I haven't had nearly as much fun as I did during Odyssey or Onslaught block. Cranking the power level through the roof and throwing the color pie out the window does not make for a very good game.