I have yet to read a negative review on any of the Era models however...
Based on the reviews and their nice design I had my eyes on the D4s for quite a while. It wasn't a question of price it's just that I was afraid the D5s would load my "difficult" living room with bass. I had demoed them and had specifically requested that the salesperson put on something with lots of bass(Holly Cole) just to see how they would handle it. Just as expected - even in an acoustically "perfect" room the bass was just too much for my taste - I could only imagine how it would sound in my untreated room. The D4s were out that day so I couldn't do an A/B comparison. A few days later I borrowed them (D4s) to try out at home. I had high expectations figuring that they should be just the right combination of small form factor, nice design and good sound without too much bass - big disappointment. Besides the really nice top end, on my 75w/ch Cambridge amp, they just weren't happening. As much as I wanted to like these speakers to me they sounded dull and lifeless. Was I expecting too much from such a small speaker or was their low sensitivity(84dB) the problem? Could be. However I did try a pair of 9 1/2" tall Proac Tablette 8s(86dB) on the same amp and it was a whole different ball game. Whole different price range too - unfortunately.
I even have and old pair of 250$, cheapish looking, PSB Alpha B1s that, in my opinion, in my room, in my system, run circles around the 600$ D4s.
But don't take my word for it.