So on my brief experience after taking delivery tonight and only using radio and classic rock I'll give it a 6.5 out of 10, This is coming from a person that has been installing custom setups since 1985. Bass needs an upgrade for sure, really a nice solid sound quality oriented 8 or 10 with 250-300ish would make a huge difference here, overall bass output is about what I got out of my Sea's 7 inch Midbass's in my 3 way active setup in the RSX but little to no actual sub-bass. Mids and tweets are about what I expected, tweets are a little better but I am not a fan of metal domes that high up, although with them being more on axis I didn't note the same type of harshness you get when hard domes bounce off the glass. Mids were pretty clear but really lacked in the midbass dept. overall highs were pretty clear but did't get that loud to me, but keep in mind I could hit the low to mid 140's db wise in my RSX.
HU is another story, with the IMID integration and the lane change and rear camera I would strongly suggest integration over replacement if you want system as it is a pretty good touch screen unit. I am going to use a RF 3sixty.3 but PPI's DEQ-8, Soundstreams Synthesis, or the Audio control deq-61 would work well, I would not use a JBL MS-8 as even though it would do a good job, you need a center channel in order to reach its full potential and there is no easy way to add that on. The lack of center channel (well and no HID's) is the one bitch I have as cheaper Kia's and Hyundai's can do one but Honda can't and with video and hdmi you would think they might think about dolby 5.1