Pros: Small form factor, accurate, flat, natural sounding, wide and realistic soundstage and positioning, loudness
Cons: Average built quality, underwhelming amps, availability, limited potentials, no height nor depth in soundstage
I stumbled upon these in the need of a studio monitor, when listening to the HD600 everyday for a few hours have made my head hurting and ears ringing quite often. But I live in a small college apartment with colleagues next to poor isolating rooms, so my choices were limited. The Japanese engineered Fostex company has again lived up to their name, with the Fostex PM0.3 (not just their headphones are good, ya know!). Incorporating a small and personal form factor, but not losing neutrality and sound quality (soundstage, lows-mids-highs, accuracy and details, etc) at the same time in spite of a 3-inch driver.
The small form factor means more room for your desk or portability for travel. Though the built quality and materials are not top notch (fake wood, plastic, PCB, rubber, nothing metallic or fancy) they are backed by a 1 year warranty (authorized retailers only). The overall construction is above average nonetheless (you get what you paid for). The built-in amps power them to sonically reproduce adequately even without a solid-state/tube preamp; they sound great and impressive right out of the box and just plugged into your computer's onboard soundcard. The sonic performance of these speakers are similar to that of some even larger and more expensive monitors (compared to the ones I've heard, a few Audioengine, Mackie, Swan, and the Edifier R1900T series, etc.); it is just unbelievable of how these sound for the size they are. While the soundstage is not the best in the industry, they do feel particularly realistic and wide enough. Instrument imaging and staging is very, very good. Sound signature is extremely similar to the audio-technica ATH-CK10 IEMs, and I am very confident in saying that after hearing between the two for 4 months, there is about a 90% similarity; the neutrality, details, imaging, and forgiving of low bit-rate files and poor sources; (2014/01/01 update edit). They are great all-rounders and perfect for any genre. The best point of all however boils down to this: you can listen to them at quieter levels, yet still hear all the details and accurate reproduction of your audio files.
Moving away from the good things, these monitors do have a few bottlenecks however: the small build leads to more money for a higher and dampening stand and walls, for the tweeter to be at the same level of your ears; the volume knob is on the back, which could be hard to reach or adjust for those who need to do so often without multimedia controls or a preamp with volume knob/control ready at hand. Personally, I think the most unfortunate drawback is while the unit has a MSRP of around 8000 yen (roughly 100 USD), it is hard to find one in North America under even 150 dollars (for around 200 USD you can get the PM0.4 (one inch bigger) which in my opinion from audition is it's only slightly better in overall SQ). For information on PM0.3 and amping, please refer to Headzone and amprepairs' comments of this review, thanks.
All in all, I recommend the Fostex PM0.3 as one of many solutions to any amateur or even professional audio enthusiasts/composers/producers who are looking for a very intimate yet revealing set of small active speakers. Please remember this: if size is not an obstacle to you, then definitely pick something else, but if you need something small and powerful, this is definitely the #1 choice. There are not a lot of small sized speakers out there that are active and as neutral as these; they even have great value if you can find a good deal/price (around $150 brand new or lower)!