It's been two years since the HTC One M8 smartphone hit the market. It's not surprising that expectations for the next-generation handset, the HTC One M9, have been running high since news broke that the device was in development and coming to market.

Initial first impressions were resoundingly positive given specific enhancements, yet more than a few reviewers weren't convinced the changes and improvements justified an automatic upgrade for those with the M8 in hand. For those still carrying around the M7, the switch is generally viewed as a good move.

The HTC One M9 is getting big points for its metal body, sleek design and improved camera features and capabilities. As one early review described it, however, the handset may be "the world's most beautiful disappointment."

Now, given more time and scope to delve into the HTC One M9's specs and capabilities, reviewers haven't dramatically changed their initial take. Android Authority's review cited the phone is thicker and features sharper edges, and that low light performance is a big disappointment, yet it also reiterates it has one of the "loveliest" designs.

"Perhaps one day we will get an HTC device with a QHD display, but for now HTC appears to be more focused on user experience, and not about the raw specifications. Considering how nicely the display continues to perform at these specifications, we're not complaining," noted the review.

Gizmodo took a more cultural assessment of the smartphone, noting that just two years ago the HTC One M7 "brought incredible disruptive energy to smartphones" and the next iteration, the M8, "ran neck and neck with the best you could buy." The M9, well, not so much, noting "it's not exactly leading the Android pack" at this point. Given time to play with the smartphone, the reviewer also noted that it's a bit "super slippery," stating "the M9 is a curse for the clumsy."

AnandTech took a much deeper historical view of the HTC portfolio in light of the new M9 offering, stating that the M7 essentially "saved HTC" in terms of relevancy in the smartphone market and at the time the M7 was a better device than any competitor.

"The One M8 continued this by refreshing the M7 in some key areas, but areas like the camera weren't really improved upon, the design was a bit too rounded, and the ergonomics of the bigger phone weren't the greatest due to the top-mounted power button," noted the review.

"Overall, I can appreciate the improvements from the M8 but I'm not sure HTC took the right direction here, as they've dramatically increased cost and reduced yield of the back cover in order to achieve an effect that may be hard to appreciate in practice. The ergonomics of the phone have meaningfully improved, but the improvements in design overall are quite subtle, and casual observers will probably view the M9 and M8 as basically interchangeable," stated the review.

A look at how the three HTC smartphones compare: