I use one on a very broad horse simply because I couldnt get a leather one to fit.
Its quite difficult to change the gullet, you need a bit of brute force. I personally dont like the synthetic feel of it rather have had leather, but others on here have favourable opinions of them
Great saddles. I've got a .gp and a dressage and I love them both. They can be adjusted really easily when the horse changes shape and need very little maintenance! Perfect and lightweight for the horse too
They're fab - if they fit. The changeable gullet doesn't guarantee a good fit - it will however allow slight alteration for slight changes in muscle / condition. But only if the saddle fits in the first place
I have 3 and really like them - but my one mare in particular did not like the cair but goes beautifully in the flock. I found the cair panels very hard and unforgiving.
They are lightweight and easy to care for, and my preference is for the top end of their range as you get proper girth straps. The lower end have horrid plastic straps AFAIK
I've got one for my NF pony who is forever changing shape - can't comment on how easy it is to change the gullet as my saddler does it for me.
I too prefer a leather saddle, but I could only afford a synthetic - I find the seat a little unforgiving on a long ride, but I just use a seat saver for my bot! Pony loves the saddle - very lightweight.
The old style (500/2000) are badly designed saddles. Stirrup bars too far forwards (puts you in a comfy 'hunt seat' , but nigh on impossible to achive a correct position). The width can be changed but the rest rarely fits anything but muscled TB's : the front gusset is too shallow for anything with pronounced hollows at the withers but the rear panels are far too sloped for anything with remotely flat loins (the outside edge digs in on anything but slopiing TB-esq loins). The tree, due to it's inherant design, becomes more and more curved as it gets widers. At much more than a medium (which is really narrow by any other brands standards) the tree is far too curved for most backs. So to balance the rocking, and to compensate the shallow front, they're usually fitted too narrow.
The new wintec model (the one with the shaped knee rolls) is a much better saddle and suits many horses. They are very hard to get second hand currently though (only recently out) and many saddlers still sell the awful old one (the changable gullet means they fit everything, right?? )
Also look at thorowgood saddles. Far better design for most horses. Same price as the new wintecs.
I Have one of these for a ISH thats a very chunky and a lot more ID. It's lasted him 5 years with just changing the gullet about a bit and the saddler checking. I find it really comfortable and low maintenance. Mine also looks leather apart from the knee rolls and under the saddle flaps