I've had mine about 3 months, and I love it. For reference, my previous car was a new Fiesta ST, and I have a 182 track day car. I currently commute about 70 miles a day on A/B-roads in it, and it's perfect for that. It has improved build quality, a more refined and comfortable ride (even with the Cup chassis option), but it's also quick in a straight line and fun to chuck about when the mood takes you. I also get about 35-37 mpg on average. The auto-box I have absolutely no problems with; I believe it was updated slightly for the latest models (which mine is), and I've yet to confuse it in full auto, and gear changes are suitably rapid with some nice pops from the exhaust on upshifts. It also makes that crawling morning traffic through town much less effort!
I admit it's perhaps aimed at a very narrow market, but it definitely has its fans, as this thread has proved. The Fiesta ST is more go-kart like and perhaps more faithful to the original hot hatch values that Renault themselves played a big part in setting, but the ride was a bit wearing for me on my commute, every single day. Also whilst the heated Recaros were good, the rest of the interior was dated and not as refined as the Clio, IMO. It was, dare I say it, more fun generally though. Every journey could be made to feel like a rally stage, it just had an eager feeling about it and with a shorter commute (and a little less Renault 'fanboy-ism') I'd have kept it.
Another point is the price. I'm lucky and had access to a 'Friends & Family' discount meaning it was actually cheaper than a Fiesta ST-3, but if I'm a member of the public who can only negotiate so far, or had a short commute and didn't need to worry about comfort, or refinement, or any of that, I'd definitely have to consider a Fiesta, or if it had to be Renault, stretching a little more for a Megane. Or just go all out for a 220 Trophy! They are genuinely very good. For me though, it fits my needs perfectly, but can see why some people are disappointed with it. It all comes down to what you want from it. Unfortunately, it does seem to have let down a huge chunk of the fanbase, but for others (like me), it's allowed me to have a Clio R.S. without having to turn to something like a Polo GTI for small hatch 'refinement' and all that, and probably won over a few new fans as well.