On 2/29/2012, the Raspberry Pi foundation came out with it's first model - the 256MB Model B Raspberry Pi. Since then several versions and revisions of the Raspberry System has came out. On its 4th Year Birthday (1st Leap Year BDay), it releases the Raspberry Pi 3. It has been a year they released the Raspberry Pi 2.
 
The P-Pi 3 has a 64Bit Quad Core (Arm A8) CPU running at 1.2GHz. It has built-in Wifi and Blue Tooth wireless modes.
 
Outside of that, it is still the same as the Raspberry Pi 2: 1GB of RAM shared with the Video GPU which can be defined by the Configuration Panel. Jessie - Raspbian from the R-Pi 2 will work on the R-Pi 3 with no modification to the boot up code. Physically, it is still the same form factor design of the Model B+ and R=Pi 2: 4USB Ports and 1 Ethernet Port. It costs the same as its predecessors- $35.
 
But many users are complaining about it. The main beef about it is it runs hot. Of course - it is running as at faster rate and a larger chip with more options, it will run hotter. It also requires a heftier power supply, though the 2amp supply used on the R-Pi should work fine with it. It would be best to get a Heat Sink set for it.  

There are problems...
 
1) Over heating because of the faster CPU, and built-in wireless (Wifi & BlueTooth). So you need to add heatsinks to it.
 
2) They say that you can take your R-Pi 2 SD Card and use it to boot it. There are problems with that because you have to update Raspbian on the R-Pi 2 before you can use it on the R-Pi 3. You can fresh install Raspbian onto an SD Card and run it on the R-Pi 3 for the updates to get Wifi and BlueThooth. A lot of Config Text files need to be redone if you go from R-Pi 2 to R-Pi 3.
 
2b) Once you do an SD Card from an R-Pi 2 and updated it for the R-Pi 3, you can't use it on the R-Pi 2 again.
 
3) Wifi turn on easily with Raspbian but there are problems with Blue-Tooth. You need to play with the BlueTooth settings to get it turned on. And Wifi shuts off unexpectedly, but that problem has been around for while already.
 
3b) Do not use a Metal or "Aluminum" case for the R-Pi 3. The metal case blocks out the wireless signals.
 
4) Other OS are hurrying up to make bootable working versions for their OSes (Like RedHat and Ubuntu). Their current R-Pi 2 version does not boot up on the R-Pi 3. The Raspberry Pi Forum has been on fire because of this. I figure give them a week to figure this out.
 
5) They say it is 64Bit. It is not. It is like what was done with the Motorola 68K - 32bit registers but 16bit databus and 24bit address bus. In the case of the ARM CPU - it is 32bit Data & Address Buses but 64 Bit registers instead of 32bits. There are problems with this and the Raspberry Community is up at arm about this. Raspberry Pi Foundation claims that the CPU can only handle 1GB of RAM but many users including me pointed out that other Raspberry Clones (Orange Pi, Banana Pi and et al) have 1 - 4 GB and android tablets running on the same CPU/GPU make up (about 97% of the market) has 4GB to 16GB of RAM on the high end market. In making my statement on the Raspberry Pi Forum, my post was deleted and I was warned not to make another statement like that again or I would get banned. I thought about doing it but decided not too.
 
At least in some systems (like Pine64) they are under the same configuration set ups - 32bit buses with 64bit registers. So far, the Raspberry Pi Out-Performs the Pine64.

Most of the problems can't be fixed, like the over heating. And the wifi issue has been around with USB Dongles from the beginning, but now it effects the internal wifi. The problem is the OS, not the R-Pi as there is some cures on their forum but not all of them work.
 
BlueTooth... well, wifi in general, does not work in a metal case because the case makes a Faraday Cage and blocks the signals. This would be interesting as the Astro Pi is in a metal case. The Astro Pi is a R-Pi set up for operations in space and in the space station for various experiments by schools and agencies. Over 200 were sent but 100 made it; the first rocket to go up with the first 100 blew up a minute after launch, destroying the supplies to the space station including their food and 100 Astro Pi's. They had to send up another batch to them and they arrived unscathed and are working beautifully.
 
Everything else is software issues with the OS. But they do not want to do work with the software. I like their premise of having a system so cheap that everyone in the poorest of nations can have it. But their implementation of it is lacking. They do not have heart to do this properly.
 
The R-Pi is built similarly to an Android Tablet - same ARM CPU family, similar or same GPU; if you search ebay, you will find such tablets with 2GB and more, many with 8GB of RAM. A few with 16GB! There is no excuse for this and they know it. And the R-Pi Clones are 1GB and larger (2GB on the Orange Pi).
 
What can I say? I'm not happy with it.