Finally got my account active here (although I'm usually a lurker anyway =P) and figured I'd post in this thread with a quick followup on the couple of reviews of the Flyknit Racer. I pondered putting this in the review section but figured that this would also be an appropriate place to post.
I'm in the middle of a pretty aggressive running program (running between 25-30 miles a week) with an average of a 10k per run. I got the shoes on Saturday and took them out for a run for the first time on Monday for a 6 mile run, then again on Wednesday for a 7 miler. For the past two months that I've been on this schedule, I've run primarily in Lunarglide 3s and Free Run 2s.
I actually found the Trainers to be as narrow as the Racers so half sizing down to accommodate the added length resulted in an overly tight forefoot fit. I therefore went with two pairs of the racers. In retrospect, I wonder if the upper on the trainers might stretch out a bit to fit my wide foot but ultimately, I'm of the belief that if the shoe doesn't fit comfortably on a treadmill run for 3 min, it definitely won't be comfortable over longer hauls. Odd as most people seem to have commented that the Racer seemed to be narrower but that was not my experience.
The upper of the racer definitely feels like a second skin and is arguably the best fitting upper of any running shoe I've owned. As was pointed out earlier, the narrow profile of the sole concerned me that my foot wouldn't sit completely/comfortably on it. Over the course of the 6 miler, I didn't feel anything out of place but the 7 miler included a long uphill stretch and there was some slight discomfort. Ultimately though, it's clear that the upper's wraparound design does help suspend/support my foot. Another note to support another earlier post is that I can loosen the lower laces to get it to fit my wide foot while tying the top lace down tight to effectively eliminate any form of heel slip.
During the run, the shift from a Lunar based cushioning system back to Zoom (I used to run quite a lot in the Zoom Victories back in the day) showed me how far cushioning has progressed with Lunar. The ride was definitely harsher that what I was used to (for obvious reasons) and the lack of support or stability was noticed on the runs. Interestingly enough, the Racer actually felt harsher than even the Free Run 2s that I was running in on easy days, although I'm not sure if that will change over the next week or so as I put some more mileage on them and the shoe breaks in. What was instantly noticeable was the speed increase and lack of effort required compared to the other two shoes. There was definitely more energy return and a faster toe off while running in these than when running in either of my other shoes. I'm not sure if this is due to the fact I had a rest day before both runs or if these being the first racing flat style shoes I've run in made the difference, but my pace according to my GPS readouts put me at almost 10-15sec/km (averaging almost a 5:19/km from a 5:35/km) faster than in any of my previous runs. I don't doubt that weight had some factor in this but that large of a difference points to something else, be it some other aspect of the shoes or the day of rest.
Durability wise, I do wonder if the Racers will hold up over repeated training sessions but I guess I'll find out over the next couple of months. The upper itself seems to be quite resilient, and the only concern I'd have is the outsole potentially not holding up well to large mileage, as well as the seam between the upper and the midsole as was mentioned earlier in the thread. Hopefully the latter was just a freak occurrence.
In the end though, I'm definitely satisfied with the purchase and, despite the higher cost, believe that these shoes do bring an appreciable improvement/change to my current rotation. I feel that these shoes are definitely not something I'd run in everyday, as the lack of cushioning does concern me a bit for long term training and potential injuries. However, the overall fit of the shoe is light years ahead of anything else in my rotation and the fact that I want to see if additional mileage might soften up the overall cushioning means that I'll probably try to fit in the shoe at least two times a week for the next month or so, albeit on runs no more than 7 miles. I'm very interested in hearing other runner's opinions on the cushioning of the Racer vs. the Trainer and if there is any appreciable difference between the two. Ultimately, it's a different kind of shoe for a different running experience that I hope will help improve my running overall by giving me something new to train with/adapt to.