Picked up my 4.5 Slick today but boom still a week or two away so used a carbon SUP paddle to get by. I'm coming from a 5.0 Unit and have used Echos before.

5.0 unit 2.2 kg

4.5 Slick 2.06 kg without boom (2.3 kg with carbon SUP paddle)

quite a bit narrower than the 5.0 Unit

Slick front handle wider

Guessing the stock boom will have a T shaped head to prevent it rotating. SUP handle fit pretty snug.

You have to squeeze the boom in before the wing is inflated.
Had a really fun 2 hours this arvo on it in 8-9 knot average 12-13 gusts. I'm 70kg on Axis 910/420 and 80L Quatro. Had to pump pretty hard to get on foil but was pretty comfortable once up. Was definitely easier to pump with the reduced width and felt like I got up just as easy as the 5.0 Unit. Stability is the first thing that hit me, it's really light in the hand. Even though it's 100g heavier than the 5.0 Unit it actually felt quite a bit lighter. Really easy to wing one handed.
Really stable depowered to, tried the front handle on a couple of little ripples and I'd say it's at least as good as the Unit. The wider front handle is a bit flatter too so your hand fits snugly, seems to help with stability.
It's a dream in heel side tacks, completely neutral through the eye of the wind, doesn't flap around at all.
Points crazy good, at least as high as the 5.0m Unit probably higher. Speed is great too.
bigtone669 is spot on about the tip hitting the water, just seems to bounce back rather than getting ripped back and flipping the wing. Great design.
Window placement and size is awesome, great city views all arvo. Never noticed them on the Unit.
Boom is way easier for transitions but never clicked with the Echo. Slick is the best of both Echo and Unit.
Spewing my 3.0m Slick won't be here till September ??????