Number One effect for me is the stereo / ping-pong echo... it is very smooth and the Diffusion settting gives it a lovely reverby gloss as the sound echoes away to left and to right.
it was my only echo box for about ten years and i used it solidly, all the time - until i bought a Line 6 Echo Pro because i wanted that filthy tape-echo sound instead. I'm constantly tempted to bring the Zoom 9001 out of the retirement box... but then why did i spent £300 on the Echo Pro :-(
Reverb as such is not an effect i use much, but the reverb here was highly praised at the time in magazines.
The rotating speaker is not bad - and can be set up to slow down and speed up between settings as the real thing does.
There's no Phaser effect, but there is a flanger - which i found too harsh for the kind of spacey Jarre effect i'd be after. Chorus is also a bit harsh, i think, but i'm not a chorus user.
Auto panning is something i used often on the Zoom 9001 and it is very - in fact, i have two of them and on complicated mixes i like to get various automated left-right effects for synth parts going into the mixer. Reverb can be added on top of panning.
Remaining effects such as the Limiter, Enhancer etc are usually biased (optimised) towards specific instruments. But there is no Compresser for the Vocal settings - though it's easy enough to use a guitar setting if you need that. Pitch shifts are OK... the Steel Guitar patch is pretty good.
No Distortion/Overdrive effect, if you're wondering, but i can repeat what a previous reviwer has said - theis unit can create some lovely recordings of acoustic guitar.
Finally, there is a test tone generator (including A440 etc) and a seashore effect!
For FUN ONLY, the Robot setting randomly changes the Harmonizer settings for a kind of instant Kraftwerk.
I have not found it to be noisy (i use it mostly in the mixer effect loop)
i've had mine from new - used, as i said, constantly (not even using the proper wall wart) and it still works completely reliably.
Only thing i found was that if i used metal jacks on the output then my "spider" wall wart plug would touch and short out....
but isn't that just my own fault!
the plastic box would not survive if you drove over it... unlike a Boss.
I like this unit so much... but don't use it (them! i have too) very much now - it's kind of replaced by the Boss SE70 and the aforementioned Echo Pro. I do still bring them out for indvidual instruments when needed and also for the occasional gig, when i need the portability and don't want to carry my rig on the train - the Zoom 9001 weighs nothing!
I wanted to put this review on, because previous have been a bit negetive - i'm really not selling my two ever, they just have so many uses and are of sufficient quality to keep them in occasional use amongst my pile of quite high-end gear.#
Would i replace if nicked?!
well... if someone nicked my Line 6 i'd just put my Zoom back in the loop and not worry about replacing the 6!