http://developer.android.com/guide/practices/optimizing-for-3.0.html

About emulator performance

Initializing the emulator can be slow and can take several minutes, depending on your hardware. When the emulator is booting, there is limited user feedback, so please be patient and wait until you see the home screen (or lock screen) appear.

However, you don't need to boot the emulator each time you rebuild your application—typically you only need to boot at the start of a session and keep it running. Also see the tip below for information about using a snapshot to drastically reduce startup time after the first initialization.

General performance in the emulator is also slow. We're working hard to resolve the performance issues and it will improve in future tools releases. If you don't yet have a real device running Android 3.0, the emulator is still best way to evaluate your application's appearance and functionality on Android 3.0.

Tip: To improve the startup time for the emulator, enable snapshots for the AVD when you create it with the SDK and AVD Manager (there's a checkbox in the AVD creator to Enable snapshots). Then, start the AVD from the AVD manager and check Launch from snapshot and Save to snapshot. This way, when you close the emulator, a snapshot of the AVD state is saved and used to quickly relaunch the AVD next time. However, when you choose to save a snapshot, the emulator will be slow to close, so you might want to disable Save to snapshot after you've acquired an initial snapshot (after you close the AVD for the first time).

To disable the "Save to snapshot" option for AVDs launched by Eclipse add "-no-snapshot-save" to the Default emulator options under Preferences > Android > Launch.

 

As to your build errors when you launch Eclipse, I would check what it says under the Problems tab in the bottom pane. I haven't been able to recreate it thus far, but then again I edited the configuration since it didn't automatically import as an Android project via Eclipse.