I'm guessing the PCR's would (in principal) work over a midi-cable even without the driver on Win10? How much functionality would be lost if someone had a midiport over and could use that method?

After using my PCR-800 for many years as a midi keyboard and control surface, I replaced it this past week with the Behringer X-Touch on my Win10 system. Very happy with my decision. The long throw motorized faders make a huge difference for writing automation to my tracks. The rest of the board is very intuitive. The keyboard and mouse are getting used less each day. The PCR will continue to be used for my midi keyboard only.
 
I deleted the PCR control surface and midi ins/outs when I installed the X-Touch. After reading this thread, I wanted to check if my PCR still works. I re-enabled the PCR for midi keyboard. No problem. Then I re-created the PCR control surface. Transport, faders, knobs, buttons...it all works fine on the PCR (using ACT), even with the X-Touch. In fact, I can move the faders on the PCR and the X-Touch faders respond, along with the faders in Sonar.
 
So, the PCR-800 will work with Win10. I'm connected via usb using Roland PCR driver 1.0.1.0 dated 9/30/13. Haven't tried any newer ones. Metz, sounds like you also have yours working too. Just thought I'd throw this out there as another option to separate your midi keyboard and control surface.
 
8/20/16 Update: No control surface function on the PCR-800 after the Win 10 anniversary update today.  Connected my PCR to my interface via midi and the PCR-800 is working fine with Sonar and X-Touch. Just can't use it as a control surface. MIDI is all I need it for now anyway.

The Anniversary update also hosed my PCR drivers.

However by turning off the Windows driver signing feature then installing the W8.1 drivers they now work like a charm. IIRC i didn't even have to hack them this time. The updated method of getting PCR drivers to work is descibed somewhere in the forum - i found the thread by Googling.

My Edirol SD20 also received the same treatment and is up and running.

Cheers,
J

I found an inexpensive M-Audio keyboard ($100).  Basic 49 key model.  Just right for my limited use.

I'm glad you guys are discussing this. I'm on the lookout for one of these too. Any opinions or experience with the Samson Graphite 49? I can get one for a great price.

musicroom
I'm glad you guys are discussing this. I'm on the lookout for one of these too. Any opinions or experience with the Samson Graphite 49? I can get one for a great price.

Would like to know this myself :)

I've joined the dinky controllers that can be used on iPads club.  I have the 3 Novation Launchkey Mini series.  My Oxygen 8 v1 still works.  If I need a serious 88 keys my digital piano works. I still have the 1st Axiom 49 if necessary. I have one of those mini IK controllers that flaked but a new usb cable from the 99 cent store fixed that.  I have enough.  My room looks like I'm a serious keyboard guy which I'm not.

I am thinking of joining the dinky club also, I was about to buy a Native Instruments 61 key, but are now thinking that I can live without afterouch, and just get a cheapy, and like mentioned above, if I need something a more serious use a 88 key digital piano, I am going to upgrade to a Casio Privia PX-5S next year I think.
I am watching for demo stock deals at a couple of online stores for a 61 key synth action, at the moment its likely to be Nektar lx61, but might go an lx88 since it has midi out on it.  Either way I get to save 600+ AUD, to spend on a nice instrument library or other gear such as an xtouch.
When I first purchased Sonar, my plan was to get the Akai Advance 61 or the NI 61 model, but now that I understand what they do, I would rather advoid them and get something more generic and risk proof, that way if they go the way of NI's Kore, well, I can just go spend a 100-200 and get a working replacement.

Don't throw out your PCR. I sold my 500 (only $80.00 but better than nothing) and got an Advance 49. Not much use with Sonar but I have a Mackie. You get an incredable amount of Air instruments and effects with it an even  a Blackhole reverb through Sept. Can't think of anything I have it doesn't work with. I love mine. With the multi you can put together, playlists and the FX. Some people thought the keys were too stiff but not for me. I'm a guitar player and playing my PCR I could bit of pain on occasion. Not bad but small pains. Never happens with Advance. Maybe keys are a bit of a shock absorber. Only thing is I should have bought the 61.

beltrom
I'm guessing the PCR's would (in principal) work over a midi-cable even without the driver on Win10? How much functionality would be lost if someone had a midiport over and could use that method?

Correct.  If all you want is the basic functionality from a midi keyboard (keys, pedals, pitch, mod), you don't need to install the drivers.  As long as the keyboard has AC power and a standard midi out, you're in business. 
 
... Unlike the newer keyboards with only a USB connection, which are totally dependent on the drivers.... If the drivers don't work (or are nonexistent), then you have a doorstop with a bunch of knobs and sliders... 
 
My ancient CME uf5 keyboard has knobs, sliders, and transport controls -- none of which have worked absent working drivers... but because of the midi connection, it's still a perfectly usable keyboard with pitch and mod wheel.