Pros: Smooth, soundstage, mids and high sound like from desktop DAC, filter 1&2 selection
Cons: Heavy, battery or chips issue, battery life, no bass adjustment, built-in amp not power enough, useless case, big annoying volume knob
Best i-Device portable DAC ever listened to, very neutral and smooth like from a desktop DAC. Currently using it with my iPod touch 5 (Yes, it's support lightinig connector). I will prefer filter (2) than (1) as (1) is more flatter. Built-in amp is not powerful enough to drives some headphones, currently I using SE535 and Bowers & Wilkins P7 both headphones sounded perfect with HP-P1.
Now battery is the most problem given to me. After 6 months I get HP-P1, the battery seems to be not function at all but under warranty my dealer change it a whole new one for me, but after a year plus the battery seems to have some charging problem, after 20 to 30mins of charging time the battery light keep blinking and won't charge at all, sent back to my dealer this time out of warranty for about 6 months, finally my dealer said that Fostex have to charge me about $323 to replace some sort of chips and board so I decided not to repair it, now while I charging if the light start blinking I have to plug out and in again to get charge.
Overall It is worth buying it? while it's depends on yourself because out there, there is cheaper and average good sounding portable DAC to choose, but if you want an awesome sounding portable i-device DAC you should give it a try, it will make your i-device becomes a Hifi i-device.