Most of the modulations (i.e. phaser, flanger, chorus, tremelo, etc.) are very good. The delays, reverbs and hall echoes (the Ambience section) are fantastic, especially the multi-head tape echo (Roland Space Echo) and echoplex models, and the stereo and ping pong delays are great for everything, including processing drum loops and samples.
I think the distortions suck. They're feeble and WAY too noisy at any realistic setting. Better off using a real distortion pedal into this baby since digital distortion doesn't cut it. The compressor is noisy as hell at all settings. The cabinet simulations are pretty worthless too. They remove ALL the bottom end--even at the 4X12 Tweed setting, which is supposed to resemble a Fender Bassman cab. It doesn't.
But the tape delays and classic modulations, especially the "Classic Flanger" (MRX) and the "Black" (TC Electronic) and "Orange" (MRX Phase 100) Phaser settings are dead on. Buying the real analog delays modeled here separately would cost a grand or more. These make this unit a bargain. Just keep the amp/distortion and cab settings off, and you'll avoid noise. Also, the Univibe and Traveler and pedal settings are pretty good. The sample and play mode is gimmicky. The wah is not worth mentioning.
No problems yet in 8 months. The unit comes with an 9v 500mA AC wall wart. It doesn't take batteries.
Good quality effects that don't sound digital. The amp/distortion and cab simulations are lame and noisy, but can be bypassed. It's best feature for gigs may be as a tuner. The tuner is fantastic and easy to use. The built in metronome has turned out quite useful too.
Check out http://www.midijamman.com/ for good patch info on this unit, especially if you want to find out the original effects Korg modeled for the AX1000G effects.