First thing first - i'm not a 10/10 on all points man - I don't know if there's anything out there i'd score like that, but I have given this fairly high (imo) scores.
I am a fan of all of arcdev's plugins - they all have their uses & tend to be straightforward & to the point - something I appreciate.

User Interface: It's simple - all the knobs you twiddle basically do what it says on the tin, if y'know what I mean.

Sound: I love old school dub, delays that one can pitch bomb etc. - this plug in does all that kind of effect admirably & has a kind of low-fi-ish grungy sound to it.
I enjoy just automating the intensity & tone knobs to put some atmosphere behind simple drum loops.
It's pretty much has a permanent send slot place for me.
It's also very nice on pads & atmospheric moving sounds, gives them a little extra something, if applied subtly & can create devastating walls of feedback if really whacked on.

Features - i've only given it a five, but that's because it's not the delay to rule all delays & in the dubness bind them.
It's a damn good [i]free[/i] bucket brigade delay & it excels at what it does, that is reflected in my score for the sound.
This new incarnation of arcdevs et delay (the et-100 being the first) does now include tempo sync & stereo, which were useful additions - just give it that little extra, in fact i've just added a point for that :D
It's not got lfo's up the whazoo, & delays that pan in five dimensions & in & out of the fabric of spacetime - it's not supposed to, imo it's a perfect dub, dubtech & ambient/noise tool which will consistnetly give one the result one desires.

Documentation - again a five, it doesn't really have any documentation, but then it doesn't really need any - it's a simple beast.

Presets - doesn't have any, tbh I don't think it needs any, although the inclusion of a few would possibly have been nice.
Just plug it in & play with it - you won't be dissapointed.

Customer Support? Dunno, it's a freebie.
One can email the dev.
The dev has also been active on kvr & the update includes features which users asked for (tempo sync & stereo) which will likely now be included in the new version of dubb box also.
I perceive these plugins to be something of a labour of love for the developer - if he listens to user requests & implements changes based on our feedback I feel appreciative & blessed.

Value for money - has to be a 10, it's free & does exactly what I was looking for, does it well & is easy to use - I really can't ask for more.

Stability - I would give it a 10, but i've given it 9 because i'm a pessimist & maybe I haven't hammered it enough for it to crash on me yet - thing is I don't think it will, bugger it i'll give it a 10.

If you like those old school delay sounds give this a try, you really can get some nice sounds of it.
Don't be put off by the synthedit tag - I was wary of synthedit plugins myself for a long time, but i've found that there are a number of very talented developers utilising synthedit & arcdev is definately one of them.
His plugins are kinda niche tools for creating specific results/effects & are great at doing what they're suppose d to do.
Oh & regarding cpu useage - it actually seems comparable to audiodamage's dubstation, which is fairly close in character from what i've seen & heard (a little 'cleaner' perhaps) - although it would be difficult for me to do a straight comparison as I don't have it installed (presently) on my daw.

By the way I made a mistake above - this isn't freeware it's donationware - a donation to the world wild life fund - that get's another mark in my book.