wow! a lot of misleading statements here in just a day.
-it's not an old cheap wolfson chip so it's not hifi? sure it would be so unexpected for electronic to progress with years ...
imo the main reason for the success of all the good old dac chips is first that they don't cost much for what they do and everybody(company side) knows how to use them. and second, that people whatever they are saying enjoy what they already know.
-battery when used as a walkman is good. I did something like 15h with 16 and 24bit flac doing nothing else than turn it ON (or just wake it from sleep pressing play) and picking an album from time to time. used like a good old sony dap battery is not a problem. and mp3 would do even more than this.
with dsp effects I went close to 10hours. sony's help guide says that most dsp effects will reduce battery life from 40 to 50%.
then there is wifi and all the mobile phone features that can kill it in maybe 2hours (didn't measure but boy it's fast).in fact it's mostly due to the screen sucking life out if the dap even in the lower brightness setting. to me the main difference with dx100 is that the f886 is happy with whatever usb cable plugged-in to charge it. that's why I believe a big external battery, or just plugging the dap when going on the web is a good compromise. usually you're not in the street as you connect with wifi, so a power outlet should not be too far away.
-about the amp section, obviously if you plan on using a 300ohm headphone, the f886 by itself won't be too happy about it. it's more than obvious that if you need power (and I mean really need, a lot of efficient phones are happy with a clip+) then dx100, X3, dx50 are the only guys delivering some nice power without an amp. that doesn't make the sony weak, or else 99% of portable devices ever made are weak (actually that's a way to see it ^_^). it's your usual dap sold as hires capable, not as LCD2 capable.
-the "tac" noise I had was on a euro version so I can't say about others, but my guess is that it will be the same for all. now it's not a real problem and it doesn't even exist for most of you. it is for me and my super sensitive IEMs as I listen really quietly to music. and I mean really quietly, I breath a certain way so that the bodily noises from breathing don't cover the music.
to put that "tac" noise in perspective, the electronic noises from a clip+ buffering(every 30seconds or so) is around maybe 3 to 4 times louder than my "tac" noise on the F886. and a lot of people never even heard the noise I'm talking about on a clip and those who did, didn't care much. the noise from changing volume on my cowon I10 is about as loud. and the hissing from a F806 was louder (but constant so you can forget it). I can't stand using a studioV because the hiss is too damn loud for me. etc ...
if you're like me you know you need to avoid the F886. If you wonder what I'm talking about then you can buy a F886 and fully enjoy it.
I talked about it because it exists, but it doesn't mean that other daps are quiet. I'm just very sensitive to those noises and as it happens, I listen to old stuff with a lot of quiet passages (no black eyed peas for me).
this tac noise won't get louder with volume going up, that's why most people won't be able to hear it unless your IEMs are really efficient and force you to listen at very low volume. let's say the "tac is 30 or 40db with my 334 (super sensitive IEM), then you listen to music at 80db chances are you will never be able to notice a little "tac" 40 or 50db quieter than music. and the less efficient the IEM, the lower the "tac" noise compared to music itself.
I hope this bad ranting can clarify things a little, as the f866 still has one of the quieter background you can find on a sony.
-I really don't think sony is willing to let us root it's dap, but you agree that whatever mess you make with software is your own when first using the dap.
-changing the battery for what? sony's batteries have been some of the best stuff since ...before I was bald. I really doubt that one could really boost battery life given the space available in the dap.
and no sony is not traditionally known to be DIY friendly ^_^.