How can I control iTunes from another Mac?

I've been using TuneConnect to do pretty much what you're after. It's got, what I consider to be, a much nicer UI that iTunes Remote Control. You install a server component on your iTunes machine and the remote component on the machine you want to control iTunes from and it just...works.

I've been running it without any issues on Lion. It ran well for me on Snow Leopard as well.

http://code.google.com/p/tunesremote-se/

TunesRemote SE helps you remote control your DACP-compatible media player from another computer running Java. DACP compatible media players include:

• Apple iTunes (Tested working)
• MonkeyTunes for MediaMonkey (Confirmed working)
• AlbumPlayer
• Telescope for Songbird
• foo_touchremote for Foobar2000
• RhythmBox for Gnome

'Digital Audio Control Protocol' (DACP) is a protocol used by the Apple Inc.'s Remote application (app) on the iPhone to control iTunes running on a remote computer. By implementing this protocol TunesRemote SE allows any desktop or laptop to be used as remote control for your media.

TunesRemote SE combines the graphical user interface of Firefly Client with the DACP control software from TunesRemote+.