I've been wanting to pick one of these up for a long time. I'm a sax player and I think I could get better phrasing and dynamics out of GPO if I played the wind instruments through a wind controller.
I have an Akai EWI 3020. Main differences from the Yamaha are that I have to use a rack mount module with mine to convert from the analog to MIDI and the keys on the EWI don't move - you trigger them by touch. I haven't used it much with any of the orchestral libraries because of programming. (I do use it with the Akai module and with my XV-5080 with the patches I got from Matt Traum. I find that this adds a nice layer on top of GPO.) You have to remember that the various wind controllers don't output midi the same way a keyboard does, so it doesn't really work to just plug in and play...
I have both and the Yamaha is much easier to just plug and play. You will really have to work to get the AKAI to sound good (IMO). I find myself going to the Yamaha much more than the Akai. The Patchman Music site is GREAT!!
I've used the WX5 with GOP and it works fine.
Here's a tutorial that shows you how to map to Breath Controller (CC02).
You also need to download the X-Custom Optional Folders (http://www.garritan.com/support/X-Custom.zip).
I haven't tried it with JABB. Maybe Gary or Tom could post a JABB X-Custom Optional Folders.
I'm not a wind player, but I got a Yamaha WX5 a few weeks ago. With just the recorder training I had in my childood, I'm able to play wind phrases with it. It sounds much more realistic than the keyboard + mod wheel combo. And it's more enjoyable, too.
I use the WX5 with the GPO (with the dedicated X-Custom presets installed). I also use it with other synths, like my Kurzweil K2500R, Kontakt, Sculpture and SaxLab. I don'town JABB yet (but am planning to own it, as soon as I can afford it).
With the settings I found (virtual slider set to -70-95), GPO's control is excellent if you don't play extreme dynamics at the attack. Just like with a real wind, attack strength and brightness depend on your tonguing, and you can control crecendo/diminuendo with your breath. Legato is very smooth.
The same happens with the Kurzweil, that is even easier to set up. No soft sliders to program, no 'voids' at the attack, whether you play strong or soft. SaxLab acts as smoothly, and plays great.
Control of other soft-synths is not very clear to me. While I assigned Breath as a modulation source for the volume, I was not able to obtain nice results with Kontakt + the special VSL edition. My WX5 is set to transmit velocity messages, and this doens't work fine with Kontakt (it's too sensitive to velocity, and prevents you to use your breath for further control of the playing note).
On the other side, if I make all velocity messages even with a dedicated Transformer in Logic (fixing them to something like 64 or 90), everything becomes little expressive. I know it must work, since GPO ad Kontakt are abased on the same sound engine, but I was not able to do it.
In the end, I find the wind controller highly recommended, especially for a wind player.
You might want to check out the new Akai EWI-4000s wind controller. I have used the Yamaha WX11 and WX5 and do not much care for them. I much prefer the Akai EWI-3020, who's only drawback is price and need to be connected to a huge rack unit. The 4000s has midi output and thus is a lot like the Yamaha wind controllers but, in my opinion, w far better ergonomics.
Ultimately with price and convenience being about the same it comes down to personal preference, but you would be doing yourself a disfavor if you did not evaluate it.