Thought I'd kick this off with a useful bit of gear that I got today, the Casio VL-1. Despite my short time in ownership, I've used it for over 8 hours already, so am aware of what it can do.
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Ease of Use
Very easy to use the basic functions (playing it, using the calculator) however sequencing takes a little getting used to.
Price
Well, seeing as it's a keyboard from 1980, the price varies. Mine was a present, but I have been informed that it was rather cheap from a second hand store, and a quick search has found them going for less than a tenner. Certainly worth the price for what it is.
Availability
As a "Vintage" or "Retro" item it could be thought of as desirable, but not to difficult to get your hands on, I tend to think that if I have one, it isn't that rare. 90% of the time it is true, and this is no exception. You can probably pick them up rather cheaply for not that much at charity shops/carboot sales/thrift shops/yard sales/whatever.
Durability
It's a second hand keyboard that's roughly 33, apart from some understandable wear and tear (the odd scratch) it's in pretty good nick. No buttons or anything have come off, and it can probably survive a bit of beating, due to its bulk. Not suggesting you throw it around like it's invincible, but it has that kind of feel that my old nokia does, like you can drop it a few times without it breaking.
Aesthetics/ergonomics
It looks very 80's, that could be a turn on for some, but a turn off for others. It's very bulky, but a neat kind of bulky. As for alternative colour options, that's mostly going to be due to the amount that the previous owner smoked, It comes in the colours "White" "Yellow-white" and "Browny-white." It isn't massively comfortable to use, as it doesn't have standard white keys, it has buttons where the keys are. They can be a little uncomfortable to play for a while at a time due to their pointy-nes.
Size
Despite it feeling a little bulky, it should be easy enough to take to gigs, it is quite long due to the large speaker. It's roughly the same depth as DMG, maybe a little thicker, maybe a little thinner.
Portability
It can run on the standard amount of 4xAA, or a 9volt AC adapter. As mentioned before, it's a reasonably decent size to bring with you to gigs/to the studio/on the bus.
Sustainability (Batteries, Tapes, Etc.)
If you're using batteries, you may have to keep buying them, this is where my limited time in ownership does not pay off. I would suggest buying rechargeable batteries anyway, especially if you're an LSDJ/DMG user anyway.
Sync-ability (MIDI Clock, DIN Sync, Clock Trigger)
no, but you can sequence notes.
Compliancy (USB Device, MIDI Device, OS X/Win, x86/PPC)
no, it just works
Integration (CV Control, MIDI Data)
no
Ease of Modification
Probably quite easy, typing "casio vl-1" into google brings up "casio vl-1 circuit bent" as one of the potential searches. I haven't researched bending it very heavily as it doesn't appeal to me, however there may be enough of a following for there to be places to by parts to mod it. As for making your own mods, if you know what you're doing then you probably can.
Personal Experiences
Pretty damn good so far, due to only have one channel of sound playing at the same time, it's going to help me vastly in writing ZX Spectrum music due to the limitations. It so far has helped me realize that I get bogged down trying to do both channels at the same time, and taking my time with a device like this can be very beneficial. Only having one channel may not appeal to some people, which is understandable. Oh yeah, the calculator is pretty decent as well.