A year or so ago I began investing in using my iPad (now iPad Pro) in live performance, via an iRig Pro interface, and I generally use both iReal Pro and Cubasis or Auria to play backing tracks while I play and sing live. It all works very well for the most part, but even though the soundsets in programs like Korg Module and Sampletank, among others, are approaching desktop quality, they are not yet at that standard. So for live tracks I mostly use my piano, epiano and synth/organ sounds from my two keyboards. But I would love to be able to use my Kontakt and other desktop software instruments live, and this will require the use of a laptop computer. I've been reluctant to do this for years, but more and more folks are using them, and/or combining it with an iPad, etc. So my questions is: For those of you already using your laptops live for music performance, what makes sense for a reasonably priced machine that has, preferably, and SSD drive for samples, good video/audio (if needed), and is thin and light enough to be mounted on a laptop stand, with or without a touch screen, but probably with one. And what else would I need in order to make this work seemlessly with the rest of my rig? All suggestions welcome. My budget would be at or below $1500, preferably below, so that may eliminate most of the custom mades out there from the usual builders. I'm all ears to any suggestions, and am hoping that if I wait a bit, that the IOS stuff will improve  even more, and therefore  making this purchase unnecessary. I play contemporary jazz, R&B, Funk, and Pop, mostly, if that matters. I would love to use my Kontakt instruments, such as the OTS guitars, live. None of the IOS instruments come close in that area.
Thanks to all that help. Or point me to a pre-existing thread that covers this extensively and is recent.
Cheers! 

Regrets, don't have an answer but I too wish to follow this thread. At one time I took my laptop and interface to gigs performing live as you are - but there's a risk to laptop damage - I was playing sometimes in rowdy bars.. I've seen other musicians use MP3 players which obviously are convenient (yet small screen). One musician friend of mine stated he used MP3 player AND kept an identical one as a backup in case the first one corrupted in live gig setting. Lastly, I've seen full 5-piece bands using iPads attached to their mic stand (around mid-thigh) and I never learned "what" the function was. I almost think one guy, the primary vocalist, was using it for lyrics, as he kept his eyes trained on it intently. Might also use it for chord changes or set lists. Best to you and INSIST  ON LIVE MUSIC!

Artists who rely on laptops generally carry redundant rigs in anticipation of inevitable equipment failure. A laptop is designed for portability, but not necessarily for ruggedness. A 3-foot drop might not hurt your ROMpler, but it will likely destroy a laptop. When budgeting, include a durable road case plus a stable stand you can strap the computer down to.
 
These are the reasons I've never used a laptop onstage, even though it's tempting to have things like Omnisphere at hand in a live situation.
 
Here's a thought, though...there are "ruggedized" laptops made for industrial and military use. They're kind of pricey, though. But I've also seen laptops made for kids that look like they could take a fall and survive. I wonder if they're powerful enough to run, say, Kontakt.

I have used laptops live since around 2004. First one was just a basic Acer 15" Then I bought a little Asus netbook around 4 years ago. I also have a few old XP beaters I use for redundancy that people have given me.  I have dropped a few but luckily they didn't fall far but into the rats nest of wires and equipment. They tend to fall over backwards because the screen makes them top heavy. 
 
Not sure your reasons for needing to play your instruments live at the gig are. I used to years ago via a full midi rig but switched to making stereo backing tracks when the mini disk players came out. I continue to use stereo tracks to this day. I use Win Amp for playback. The beauty of this system is I can use a very basic laptop or any device to play the tracks. There's another thread going here talking about live playback gear. Look for the topic using a 2-1

Dell XPS 18, fits on a music stand! Has room for 2 internal SSDs, USB 3....