Yes I did although it was only pushed on a carpet. I have some photos but they aren't online yet but should be soon.
The BJCMGT seat is huge - absolutely enormous. Loads of height, leg room, seat room etc. The handle is great, the brake is fab. Its a shame there is no parent console like the Elite but I knew there wouldn't be. The rear access to the basket seems much better. I loved the adjustable handlebar. The hood is huge but rather strangely seems to be low down. I need to dig my BJCM out and see where it sits with my 3 year old to relate. I dont think its any different TBH but when compared to the Versa where the hood was higher, it was noticeably low at the front, but I also think the seat is bigger. I have measurements but need to sort everything out. I had two days there so am trying to wade through stuff today. There are velcro tabs on the peekaboo windows which is a little bit of a shame. Its a minor detail but makes a difference. The autolock is easy enough to do. It feels more logical than say the B-Agile one although the autolock has 2 notches on it. One of the pushchairs we tried - we think it was the City Mini - drops onto the furthest notch, so catches on the first notch on the way past which was annoying (you are having to undo the catch twice) but we were so busy that we can't remember which one of the 3 we tried did this. But the autolock can be removed by unscrewing it.
Having all the BJCM3, BJCM4, BJCS, BJCE, I think its more like the Elite in feel but without the heavy weight for carrying. It felt a little back heavy - not as much as the Elite does. I push down on the handle a bit when pushing but ihateparties came with me and she said the same. But its not as bad as the Elite is. I did put my 3 year old in the seat yesterday...and stupidly I didn't give it a really good push around, but I did push it and I can't say I noticed any issue then with 17kgs in the seat!! So to be honest I think it probably isn't fair to comment as such until one can be given some proper test runs.
As soon as I can share more info and photos with you I will. I have to say I was worried that the GT wheels would be large ie add bulk to the fold etc. But they are really dinky but yet enough IYKWIM.
I really liked it. Given I currently have both the Elite and BJCM4, I can see it replacing the Elite quite happily although I personally still like the stability of 4 wheels - but the Versa was pretty awesome and I can see my BJCM4 being swapped for that!!