I have the HTC One Defender, it has a harder inner case with a soft outer case that makes it much easier to grip the slippery smooth HTC One. The screen protector produces no glare, but is prone to get smudge marks, but this can be remedied by easily wiping the screen protector, and is a small price to pay for scratch protection. The holster and clip is super useful if you are an active person, just note the clip is not super durable and may break, but if this does happen Otter Box will replace it within the warranty period.
Overall the few cons on the case barely outweigh the huge positives. If the warranty ran out and the case broke, I would still buy another one.