Have you done some kind of modification? Some sort of software optimization or somethIng? Because I've got the base model and man. I have a couple tabs, few images and photoshop open and the damn thing lags like a mofo.
No. It was afresh Lion (10.7.4) install two days after I got the machine to deal with formatting my boot disk into two partitions, with a migration from a clone of my Lion machine's drive (since I couldn't do a Firewire target disk mode transfer). Then an installation of Mountain Lion on top of the Lion 10.7.4 instance.
The only thing I can think is non-standard is how I handle my user home directory. I always set up a boot partition and a data partition (which I name Clients). I put a /Users/myname directory on Clients and point my user home directory there. I keep an admin user with a home directory on the boot volume so I can get into the OS in the absence of the Clients volume. This setup allows very fast disaster recovery,since I keep a clone of both volumes on an external drive. I can erase and restore the boot volume without affecting any of my user data.
It doesn't seem like that would influence a performance lag issue. I can work from the admin account to test that though. A more likely culprit may be memory.
The only other non-standard things I have running are these preference panes:
globalSan iSCSI (for working with iSCSI SANs)
Paragon NTSF driver (to mount NTFS volumes read/write)
Citrix online plugin (required for a client VPN)
Launchpad Control 1.63 (Andreas Ganske's tool to organize apps in LaunchPad
Perian, Divx and Flip4Mac (Audio/video translation stuff)
Flash Player
Tivo Desktop
I also run a Java thin client for SSL VPN called NetExtender from SonicWall (now Dell). And Yojimbo from Barebones is usually always running.
I suppose I could kill them all and see if I start having a lag issue, but it seems unlikely.