Has anybody had experience with the Orions?

I have listened to a pair of Orions. Generally, I've been particularly interested in open baffle spkrs for quite a few years (ever since I listened to "Audio Artistry" spkrs, also designed by Mr Linkwitz) and have frequented the Linkwitz site assiduously.
Following your questions,

they are the closest thing to live music available

I would rather say, they are very close to what is contained in the source material -- what comes out of the phono or the cdp, etc. Having read some of your posts I think you understand the difference. There is an easily perceptible lack of distortion and, an impressive simulation /rendition of dynamics. The dynamics surprised me: the drivers used are quite conventional (OK, selected for their linearity and distortion characteristics, but still off the shelf);
the implementation extremely complex (the xover, 6-8 amplification channels).

Still, the dynamics reminded me of horns -- i.e. far away fm panels.

excellent sub-bass response within an open box

No, they won't go that low. IMO it's a good thing: bass (& sub-bass if necessary) is best implemented independently and separately, away from the main speakers in the listening room.

a very slender and elegant cabinet

There is a good point here: given the sound they produce, the speakers are quite reasonably sized.

Please note that the Orions I heard had the front tweet only. Lately a back tweet has been added.
Cheers

Actually Jmaldonado you could probably build them for a very modest investment... The drivers are about 1,5k altogether. The xover is very complex for a lame diyer -- but shouldn't be a problem for you.
Mr Linkwitz only charges ~300 for the full technical design & schematics.

Gradients are dipole only below 200 hz and i assume Orions are some where around that

No. The Orions are open baffle from ~2,4kHz to ~40Hz. Now they have a back firing tweet too (the tweet used has its own back chamber).

according to Mr. Linkwitz they are capable of conveying the full range of acoustical spaces, from dry to wet. Can anyone confirm this?

Yes, the restitution is palpably correct.

I've not done an A/B comparison. It's not easy to disconnect the rear tweeter without removing it. That would reliably reveal the differences.

Fair enough -- but, does it really matter:)?? Just enjoy, say I.

Seacard -- if you're looking for head-on, real-time, shoot out... I can't help.

OTOH, I've experienced both at close intervals and reminiscing my impressions -- they are quite different, the Orions being at a different reproductive level.
Of course, these were the older Eidolons & Orions w/out back tweet; the amplification was different as you'd expect ; Spkr positioning "agent" was identical (i.e. me, for what it's worth); I'm not implying Avalon makes mediocre spkrs -- quite the contrary, and anyway I like their products (particularly the Eidolon).