I've upgraded. I finally got tired of the rumors of the iPad pro (of course, right before it actually became a Real Thing) and got myself a bigger screen. In addition to always feeling less than satisfied with size of the iPad, I was getting increasingly frustrated with the tools available to write on my music. My 3rd gen retina iPad was getting slower and I refused to upgrade to a newer one with the same size screen and the same no-real-pens issue.
I stalked craigslist for a while and found just the right deal on a Surface pro 3. I had initially considered upgrading myself to a Surface pro 3 as my primary computer, but realized I have no desire to haul my primary computer around to gigs and plop it on a music stand. Since this machine is a dedicated music reader, I got the low end 64GB i3.
I was thisclose to getting a Surface (not pro), but I'm really glad I held out for a pro version. Turns out, while the surface is a little more square than the standard widescreen, it's still taller than a regular sheet of paper. So, while the screen is more than two inches bigger, you don't gain as much width as you'd think. I was concerned about having something with a fan in it on stage, but with the i3, the fan rarely comes on, and I've never heard it spin up in the context of reading.
The real gains come from getting that extra bit of the next page showing at the bottom. With the PDF reader I'm using now (Xodo docs, more on that later) I can use a continuous scroll mode and use the air-turn to scoot up a little bit at a time, meaning I'm seeing plenty of what comes next.
You'll notice the color difference. This is with both screens at the same brightness (about 50%). The surface doesn't get quite as bright. It's been a little more dim than I'd like at a couple of outdoor gigs, but for more orchestral work, indoors, a mid level brightness is just fine.
The biggest difference is landscape size. The Surface is just way bigger. It's still tall enough to get enough lines of music, and with continuous scrolling, I can move the music up as I feel like it. I never could get used to how Forscore scooted music around in landscape and couldn't really use it that way. The Surface set up is much more usable in landscape for me, even though I still read in portrait most of the time.
The biggest boon to switching to the Surface is the pen. I just pick it up and draw. No long press on the screen to bring up the drawing tools, dealing with either the really poor ability to draw small enough with a capacitive stylus or digging through stamps, then switching back to reading mode, usually with some wrong taps along the way.
I'll be interested to see how the music reading apps on the new iPad pro work with the Apple Pencil. With the surface, I pick up the pen, write what I need as accurately as if it were pen on paper then I set it back down on the stand. While there is an edit/annotate mode in Xodo, you don't need to open it to just write.
Pick up the pen, write, set it down. If it's any more steps than that, it takes too long and can get disruptive in a rehearsal. Getting back to that workflow in rehearsal has made the switch so worth it.