Other considerations.
I have nozero tolerance for laggy netbooks and I think thier day is done anyways, so I didn't include them.
I put most tablets into this category, but have no recent experience with them. Has this changed?
My view on a $1,000 surface pro 4 is that you should compare it to purchasing a laptop for serious use plus a tablet for its portability.
I have low tolerance for device proliferation. I don't need dozens of devices all to do slightly different things.
I recently upgraded my tablet from an old faithful (but yes, definately laggy) Asus T700. It was indeed laggy but OK for it's day. The worst problem that it had was true to all older tablets and even some new. Older versions of Android lacked a trim feature for the SSD and so it grew annoyingly slow over time. Eventually, I got so mad with it that I chanced rooting it and upgraded to Jellybean. It had built in trim and after that all was good (but still some lag.)
My new is the Samsung Galaxy Tab S (the "S" being the important part.) It's has an 1.9GHz "octo-core" with 3 Mb of RAM. I'm only 2 weeks in but so far it has been very snappy with everything I have asked it to do. Zero lag so far. I have lots more to say about it, but I'll cut it short here unless you are interested. My bullet point was, No Lag.
Regarding the Surface Pro.
I've only toyed with my co-workers. He is satisfied with it as his travel device. His laptop is obviously faster but the surface is not exactly "laggy" either if not overtaxed. It does everything he wants it to do for short stints.
What he tells me is that if he has extensive keyboarding to do, he takes his laptop instead as he finds the cover/keyboard to be tiring to use over time and a bit harder on the fingers. His job does not require much multi-tasking. I'm not sure I could do my job on it. I never have less than 10 apps open and one of them, "Netformyx," is a HUGE resource hog.
If you do serious computing, I agree with those who say above that there is still no substitute for a good laptop. My tablet is strictly a recreational device. I'd never do my job on it but I'd sure miss it's convenience if I didn't have it.
