Our initial plan was to go entirely paperless but the exingencies of satisfying transfusion services requirements and keeping processes simple led us to opt for always printing a request from for all path requests.
I think we are probably using the same supplier as you DeeJay but have opted to do without the perforations as it is easy enough to fold the forms in half for the limited duration of their usefulness. We have not started our GP rollout but for our first two planned sites one will be using a dedicated central printer for requesting and the other already uses softcopy versions of our current request forms to print requests in the consulting room.
The solution to using windows print is to define a second version of the printer in Windows with a fixed tray, (probably the manual feed) which the GP can fill with request stationery as required. This printer is given an obvious name - e.g. 'RequestForms' so it is obvious to the user which printer to select.
We have tried this in the IT department and it seems to work ok and I am hopeful that neither of the above approachs will cause the users difficulty.
We have opted for labels at the top and we had some difficulty arriving at a design that will allow for the couple of mm misalignment of paper that most printers introduce.

Ahh, the paperless environment :-)
I have had many discussions with different folk about paperless requesting. The main question is usually, "hang on, you said electronic order comms, why do I need to print forms?". In therory, that's a valid question, in practice, it's entirely different as the number of variables that can mess things up are far too numerous to make it a safe practice.

It's quite some time now since this thread was started and I now have 85% of practices on board with this. After the initial grumbling about changing paper and other issues, most places seem to be happy with it as it stands.
Labels at the top is a much better option, makes alignment so much easier.

What has become evident is that every practice works differently and the beauty of this ICE system is that one can work around the mechanism to fit in with how the practice works. I have sites that:
a) GP prints forms and gives to patient
b) GP writes details on paper, patient then immediatly goes to see AP to be bled. AP makes request on GP system and prints forms.
c) All requestors print to a dedicated central printer with ICE stationary in both trays. Patient then goes to reception to pick up forms
d) GP's make request but press cancel button rather than print button. Patient then makes appointment to see practice nurse. Patient attends again, nurse accesses request in clinical system, launches ICE and edits the request to produce forms - this works really well but relies heavilly on nurse knowing what they are doing.

All very different but all seem to work