Got it about a month ago and so far I am very satisfied with it's preformance.
Before 640 XL I was using 630 and I actually did like the 630 at first, but it slowly became outdated and the main reasons that I went away from it were just 512 MB of RAM, poor rear camera without the flash, it didn't have a front camera and the screen wasn't really fantastic. It is not comparable to 640 XL in anyway, the only thing that was sort of good was the price of 630.
The 640 XL has a gorgeus display compared to the 630 and I figured out I like phones with larger screen more than the ones smaller than 5.5". At first it did feel a bit awkward in my hand because I used significantly smaller devices previously, but I got used to it and I really really like it (when I will be buying me a next phone from MS it will definetley be an XL version or with other words, larger than 5.5"). Also, not to forget the glance screen and double tap to wake which are also two features that I really really like.
As it goes for the OS and battery life... I bought it just a day or two before the Windows 10 Mobile was realeased so I can't really tell the difference between preformance on Windows 8.1 and Windows 10, but I can say, for sure, that battery life on build .218 is a lot better than on initial version which came with upgrade (.164). I really like the Windows 10 Mobile UI and Cortana and the UWP apps like Outlook Mail and Calendar + Groove Music.
I use the phone for quite a lot, and I burn approximately 35% of the battery per day. Yet, I charge it every night, because I had bad expirience on 630 with not charging it daily.
I am not really a very good photographer, but I still like the pictures as the camera is significantly better than the one on 630. Rich capture (HDR) really does it job, though at the low illumination of places it does work slow and it did take a lot of time to process the images which was a bit irritating but that was just one situation where I was literally taking pictures every 5 seconds. To be honest, I didn't test the front camera yet in detail, but for casual selfies and Skype calls it seems to be pretty nice.
The speaker is much louder than the one on 630, but it is still not the strongest one (rock songs suck if they are not loud in my opinion) and the sound quality is better aswell.
Compared to the 630, the 640 XL is despite it's size surprisingly lighter and thinner. It feels really nice in the hand, but it takes a day or two to get used to it if you were using a smaller phone before. I ordered
the flip shell from MS store and so far I am satisfied with it aswell, it covers the screen nicely, though some people didn't figure out that they had to take off the original cover and then put the shell on the phone. The shell does make the phone a bit more thick but in general it feels the same as the original cover.
One thing that I miss on this device is the camera button. Even if I am not a really good photographer, I would still appreciate to have a camera button which would really make taking pictures easier.
The main reason I went for the 640 XL was that in reviews I've read a lot of negative stuff about the 950 and the 950 XL and because I am pretty low on the budget nowadays. I still sometimes think that I should've gone with 950 XL, but then I remind myself that MS will most probably launch a Surface Phone next year, which will probably be even more polished than 950 XL so I might ditch the 640 XL then, though it will still be an amazing phone.
Bottom line, the only negative points of 640 XL are:
- It does miss camera button
- Taking pictures can be slow sometimes
- It doesn't have AMOLED screen and Wireless charging, but that's not a deal breaker for me
And the good:
- Sharp display
- Good battery life
- Windows 10 Mobile upgrade available
- Excellent value for the price