I have seen a lot of commentary on heat issues and WiFi connectivity issues. I don't have any issues with overheating, probably because I have the i3 processor. I did purchase and use the Armor Guard case sold on Amazon, and have temporarily removed it to check for overheating issues and I didn't notice any. I have heard the i7 gets really hot, while the i5 is not as bad.
I have no problem with WiFi connectivity, which some have commented on having. Microsoft apparently addressed this with an update about the same time I received my Surface a week ago.
Before I bought the Surface Pro 3, I considered other alternatives like the Lenovo Yoga and Acer Switch, and a couple others. I'm glad I went with the Surface. It's an elegant device, and very well built, in my opinion. I anticipated the limited storage on the device, and use a micro SD for additional storage where I save my downloads, and other files that I want to have access to offline. Because there are several options out there for online storage, this was a good choice for me.
The 64GB on my device is a little over half full with 27.4GB free of what the system sees as 53.7GB. I have a couple of large printer drivers, Office 365, a couple of VPN clients and some other minor utilities installed. Out of the box, there was about 30GB free before installing the software I now have. The i3 Processor is plenty enough for what I use the device for; email, online browsing, and Office apps.
I also purchased a keyboard cover, which is very nice. I'm not an avid typist, so find it very easy to use. Those who are used to larger keyboards may not like it as much, and the on screen keyboard is useful enough to do with out a physical alternative. I DO think I would miss the keyboard if I didn't have it, and wish MS would include it with the device.