I know it's only just been announced, but it looks like samples have been reviewed under embargo because full reviews are already appearing:
HTC One (M8) review | Phone Reviews | TechRadar
HTC One (M8) review: One and only - GSMArena.com
HTC One (M8) Review
http://www.pocket-lint.com/review/128011-htc-one-m8-review
http://www.engadget.com/2014/03/25/htc-one-2014-review/
http://www.theverge.com/2014/3/25/5544642/htc-one-review-m8
http://www.gizmodo.co.uk/2014/03/htc-one-m8-review-a-one-two-knockout-punch/
http://www.zdnet.com/htc-one-m8-review-more-metal-same-limited-detail-ultrapixel-camera-7000027643/
http://www.cnet.com/uk/products/htc-one-m8/
http://www.androidcentral.com/htc-one-review-2014-m8
http://www.anandtech.com/show/7893/the-htc-one-m8-review
http://www.androidauthority.com/htc-one-m8-review-363716/
Google Play Edition:
http://www.droid-life.com/2014/04/03/htc-one-m8-google-play-edition-unboxing-and-quick-look/ (thanks KOLIO )
HTC One (M8) review | Phone Reviews | TechRadar
HTC One (M8) review: One and only - GSMArena.com
HTC One (M8) Review
http://www.pocket-lint.com/review/128011-htc-one-m8-review
http://www.engadget.com/2014/03/25/htc-one-2014-review/
http://www.theverge.com/2014/3/25/5544642/htc-one-review-m8
http://www.gizmodo.co.uk/2014/03/htc-one-m8-review-a-one-two-knockout-punch/
http://www.zdnet.com/htc-one-m8-review-more-metal-same-limited-detail-ultrapixel-camera-7000027643/
http://www.cnet.com/uk/products/htc-one-m8/
http://www.androidcentral.com/htc-one-review-2014-m8
http://www.anandtech.com/show/7893/the-htc-one-m8-review
http://www.androidauthority.com/htc-one-m8-review-363716/
Google Play Edition:
http://www.droid-life.com/2014/04/03/htc-one-m8-google-play-edition-unboxing-and-quick-look/ (thanks KOLIO )