The IPAD is good at what it sets to do, random very light computering and looking fancy. I think it is more of a toy.
The surface; however, in my opinion, fails as a laptop replacement.
While I had the SP1 and now have the SP3, both of which are irreplaceable. I can agree fully with that statement. As a laptop, the SP3 comes really close. But does fall short. The keyboard while very much improved, and lack of actual hinge don't compare to my MacBook pro retina 13 that I had. I say had, as windows is my eco system, and even with boot camp and parallels, I just found myself 95% the time in windows. I wanted the Asus zenbook, but out of stock, and tried out the Lenovo yoga pro 2 (and the yoga pro 3 looks really nice). Laptop wise, the Lenovo isn't the best but it was a very good experience. Quick note, the yoga as a tablet is crap. But as a laptop I really enjoyed it. But back to the point. The surface as a laptop and laptop ONLY isn't as good as other ultrabooks. Internals being similar aside.
As a tablet, the SP3 also comes really close. Not the same as the iPad, with battery, weight, or apps. But as a 'functional' tablet, it comes pretty close.
Now it is the closest thing to being the best at both. Foldable or detachable tablet/laptops other than the surface just don't come close to the surface. And although close, the surface isn't the best at either 'solely'. Actual tablet is better as a tablet, actual laptop is better as a laptop.
The whole two in one thing, I don't know. It is nice not having to have to bring both laptop and tablet, if I didn't have the surface. But if that's truly what I needed, a tablet and laptop, id prefer to bring both.
But I don't need a tablet, I have a phone. Its not as big no, and its a WP phone so it doesn't have the apps. But I don't play on apps, and everything I use, is available on windows.
Now where the surface pro 1/2/3 (and they've gotten better each generation and 12" with 3:2 aspect killed it for me, in a good way) are irreplaceable for me, is as a pen input pc. I write notes, as its easier for me and I retain more/faster when I write vs type. And I also write a lot of schematics and ladder logic diagrams. I have the note 10.1 which worked great for that. But upon first trying one note on a surface, I realized that snore had nothing on OneNote. This is just for school. For work, in the field, being able to take notes on machine performance temps ect, without having to write them in a notebook, and then plug the surface into the PLC controller and upload new programs, or troubleshoot the current program, without having to pull out my laptop and do a balancing act holding laptop left hand while trying to type/trackpad with right. The ability to pull up schematics/manuals/guides and view them full screen on a tablet, the same tablet as I do my notes and program with, is so much quicker/easier than pulling out binders and sorting through.
I can honestly say the surface pro line saves me hours of time wasting yet needed work every day. Whether at work as a electro/mechanical engineer, or while going to school for my engineering masters. Honestly, for what it actually does and time saved and organizational opertunities its given me, its worth a whole lot more than the $2000 I spent.
I'm a big tech guy. Full blown self built home workstation pc, new MSI workstation laptop stripped and rebuilt, MacBook pro retina 13 (gave to wife), Lenovo yoga pro 2 (sits collecting dust), Asus G750 JZ for the very seldom gaming i do, Asus t500/100 (now collecting dust), note 10.1 (only used to play rage of bahamut lol), all of this bought within last 18 months, all serves its purpose (or did in the case of the dust collecting devices), and 90% of my time is spent on the SP3. That says a lot, at least to me.