@Pbgoose has one so he should be able to chime in with some thoughts. I used his a few times and very different to a DE but enjoyable. Didn't enjoy the large head but a well built razor overall.
Which head did you choose @Gargravarr ? Level 1 or 2?
I love my Sabre. If you are going to compare it to the Vector then the Sabre will lose. It's just a different shave to an AC type blade razor so I think it should carry different expectations. If you enjoy a GEM blade shave then this is a very good platform to do it on. Sometimes I just feel like pulling out a GEM type razor. Sometimes I'll use a vintage GEM razor which are very enjoyable and certainly provide a unique experience.
The beauty of the Sabre is the compact head (compared to other GEM type razors). This was the first design to cut down the head post which allowed a centering/mounting of the blade above the handle. So for a GEM type razor it is quite nimble. I was a little sceptical of how the cut down post would go but find it very reliable (not entirely idiot proof but reliable).
The other thing I love about the Sabre is it's clean simple lines and profile in stainless which make it extremely easy to clean, unlike it's vintage cousins which are a comparative nightmare to clean with many grooves, recesses and edges, they are a bit of a contraption. If I had to criticise the Sabre is it lacks the distintive acoutic resonance that comes from the pressed metal shell of the vintage GEMs, but that's the trade off of the longevity and clean lines of stainless steel.
The first time I saw pictures of the 1912 pattern GEM razors I was repelled thinking I'd never buy one as I was sceptical as to whether I would be satisfied they could be cleaned to the point I would be comfortable using them. I'm glad I did try them due to the unique shaving experience they offer and because it primed me to try the Sabre when it came along.
I find the shave from my Sabre (Level 2) efficient but not aggressive. Maybe similar aggression to the Vector but not quite as efficient.
I'll be interested @Gargravarr to hear your thoughts on the Sabre. It's been a number of weeks since I used mine so this has inspired me to line it up for tomorrow.