Logitech K830 HTPC keyboard

I recently got a Logitech K830 HTPC keyboard. Have not got a lot of time to play with it but here are some quick observations:

+ just WORKS with Linux (Kodibuntu = Lubuntu 14.04)*
+ Illuminated keyboard **
+ mouse pad on the keyboard
+ mouse pad recognises multi-finger gestures on Linux
+ well made: sturdy, and slim
+ unifying remote
- no indicator for Num/Caps lock
- non-replaceable battery

Has anyone tried to open it up and see what kind of battery it uses? From experience of using other mouse with unifying remotes, I expect it to last a long time between charges.

One thing that I can't understand is the illumination of multi-function buttons. One the product page, Logitech show the red/orange text illumniated (see image below) but mine does not. Is it a software function?

PS: this keyboard is a huge improvement in quality over the k360 graffiti family.

* - official specs on Logitech site do not list Linux as a supported operating system. Custom keys might not work, but the rest functions perfectly.

Logitech M515

Picked up a Logitech M515 mouse from Bureau en Gros/Staples ($40). The mouse is sealed at the bottom, except for the On/Off switch. It has one of those "unifying" receiver for the wireless function.

Here the main points:

1. Scroll-wheel does not do the middle-click: if you do the middle click, it toggles the scroll wheel to free scroll or clickity-click wheel. The middle-click is done by the [o] button near the wheel.
2. The specs didn't indicate if it is SFF or full sized mouse. It is a SFF or laptop mouse.
3. Unifying feature cannot be setup in Linux. As indicated in the document on Logitech Unifying Receiver, Unifying software does not support Linux. You have to setup the unifying feature separately e.g. setup on Windows and then reconnect the receiver and to Linux machine. I did it on a virtual instance but lost the cursor during the setup. Restarted VM and both worked fine.
4. M515 is designed for couch (read cloth), so it might not function on glossy surfaces. Mouse pad, sofa, table top and paper worked; blue-ray player cover (black), glass, and fridge surface did not work.
   
5. Logitech says that it is active when you hold the mouse. They don't lie and it is advised that you hold it properly as I noticed that it stopped functioning when holding lightly with two fingers. You can easily test by pushing it with one finger.
6. I like the smooth scrolling wheel, but the M510's form factor suites my hand better.
7. Works even if you are 3-4 meters away just like the M510.
8. Lacks the extra buttons on the M510.
   

One important question which comes to mind is the cover at the bottom. It consists of two parts: regular grey plastic cover on the outer side (see image) and the shiny dark translucent plate covering the laser inside. Over time, the shiny central part is going to get scratchy (it is not hardened glass) which would affect the performance of the laser. Would the scratches be enough to cause scattering of the laser so that the mouse gets confused?

Still deciding if it stays or goes back.