I came across the Pico System III Eurorack version and it seemed like it could be a great first module for a Eurorack system, however after searching around (including in this forum) I found very little evidence of ANYONE using this in a Eurorack.
-- hurphendale
There are reasons for this. First reason is that the Pico III isn't a "module". It's a full synth. It has modular architecture but it's not a true module, so it's a wee bit off-topic for MG. Also, most savvy users here don't wind up cab-mounting their Pico III or other cased-but-rackables because, well, it's a waste of money and space to rehouse and repower something that already has those things from the factory.
And the third reason only becomes a problem if you have fat, sausage-y fingers; when you space a pile of 3 hp modules all together as one like that, tweaking the controls is a BITCH...and things such as VCF cutoffs and the like BEG to be tweaked. 2 hp and 3 hp (and some denser 4 hp) modules are great for hole-filling, but they're best left to things that don't require constant attention, such as VCAs, etc.
I'm with Jim above on this...but to add one other salient point: unless you know how something like a modular (or anything else!) will fit into your workflow, and how it can enhance your music, you might want to go with a prepatched rig, or some of the more interesting tandemmed prebuilds that are starting to appear. More expensive, sure...but if I were about to dive into this, I'd rather spend a bit more money for something of a more complete system...something like a Make Noise 0-CTRL/0-Coast pair, Pittsburgh's Voltage Research Lab, a Kilpatrick Phenol, Soundmachines Modulor114, etc. Even one of Korg's new ARP 2600 FS would be optimal here (save for the fact that they're quite unobtainable, something which Korg deserves LOADS of flung poo over, still!) The Pico III is OK for what it has, but more $$$ does tend to equal a more comprehensive synth in most cases. But first, determine where this would fit in what you create. Otherwise, this can be a hella expensive Pandora's box to open!