Pros: crisp and clear sound, warming bass boost, nice build, great price
I bought the FiiO E10 Olympus to pair with my Sennheiser HD 280 Pros for music production work (primarily classical music). The 280s have a sufficiently neutral response to make them useful for monitoring purposes and testing mixes on balanced 'phones. The rig they were connected to had a terrible Realtek chip inside it which was doing disastrous things to the audio channel. The FiiO E10 has rescued me from that at a very decent price. Individual instruments and tracks now leap out clearly, as does the fine detail in the recordings - the sound of a bow stroke, the little "ripple" as a trombonist hits their first note, and so on.
The FiiO sounds pretty neutral to me paired with the Sennheiser's. Some have complained that the E10 makes the mids too forward. Perhaps this is actually countering the Sennheiser veil. Although to be clear, I personally do not really hear said veil myself. In any case, the FiiO is more than good enough for my purposes, giving me a detailed uncoloured sound.
The 280s and the FiiO are okay for recreational listening. For me they are almost a little too clinical. The FiiO doesn't warm the 280s at all (which is exactly as I wanted it to be). So if this combination is for recreational listening your mileage may vary depending on what you're looking for. Having said that, if you'd like to hear a nice neutral balance with good detail for about £200 all in, then the FiiO and the 280s could serve you well.
There is also a fantastic bass boost switch on the FiiO which does pump up the lower frequencies in a very pleasant and restrained manner. The effect is very subtle, but you'd certainly notice the extra oomph on a bass drum hit. Great if a piece is just lacking a kinetic punch on the neutral response. Build quality is also very nice.