I think this a great phone. However, it's also underrated. It doesn't get the attention it deserves.
I've had this phone for 3 months now, here's the good and bad:
Good:
- Size, fit's well in the hand, while still has a generous 4.3" screen
- Battery life, at 2000mAh paired with the efficient s4 processor, it has good battery life. I easily get 20 hours. This is a HUGE plus.
- Fast. The S4 is a really good processor, same one that's in high end phones.
- Build quality. This phone feels solid.
Bad:
- Screen resolution. At qHD, it isn't quite up to par with current phones for a 4.3 inch screen. If the screen was only 4", it would have been fine. But it's something you can get used to. But, I suspect that the low res helps with battery life.
- Below average camera, shutter speed is slow, and video recording is low quality. The HDR mode is actually really useful in low light conditions.
- Very little dev support, there are very few roms for this phone
Subjective:
- UI is very close to plain AOSP style. This helps it cut down on bloat and improve speed.
I've had 3 htc phones previously, and this is my favorite phone by far. Razr M is a joy to use because it's so fast and smooth. In fact, it works so well, I wasn't in a rush to root it, I usually root my phones right away.
I've been getting a new phone almost every year, but with the RAZR M, I think I'll be happy with it well beyond that.