I can thoroughly recommend the Surface Pro 3, I 've owned one for 9 months and I also own an IPad. The Surface has replaced my laptop as my work device and will be making the iPad redundant soon. The touchscreen works well with either your fingers or the Surface Pen and it's really good for giving wireless PowerPoint presentations.
The keyboard/cover works pretty well although you can also use a docking station and alternative keyboards. Windows 10 will improve the way it works as the Apps v Desktop integration will be better.
It's very similar to the iPad with regards to its 'instant on' boot time and use ability, you don't need a huge selection of 'Apps' as it'll run any of the the thousands of Windows applications that you're used to and very quickly too.
It's not as intuitive as an IPad if you're new to Windows 8.1 but it doesn't take long to get the hang of it. The screen is superb and the fold out stand works very well. I'm not sure if it's worth waiting for the Surface 4 as there's not much to improve on if you want a 'jack of all trades' tablet.