Just a bit of advice.....
1 - I don't think anyone here has shot an Isis, as they're not available yet, so finding an informed opinion on the matter would pretty much be limited to PowerLyte themselves....unless they snuck some out to a few lucky ballers.
2 - I wouldn't ever buy a Gen 1 item ever again. From DVD players to MP3 players to E markers, Gen 1 electronics usually have bugs or some kind of fault about them that is quickly cured with a software update and/or a new solenoid, and once that happens, your new $550 ISIS turns out to be worth about $350 on the resale market (although market demand can fetch more if the item is really limited in the newer quantity, reference the AKA Viking for an example of how this works out).
Both PowerLyte and WDP, from what I've seen so far, offer good customer support.
That being said, $550 for an LCD Angel sounds like the average price for said marker. I've seen better deals, I've seen some people get taken for more. Angels have really come down in price since the advent of the Impy, the E cocker frames (Race and Eblade) and the lvl 10 in the Mags (especially in the E and X mags).
But who knows....the Isis could be the next Viking (as far as popularity and "in demand" label).
I like what PowerLyte has done so far, and they definitely produce quality products, and I think they try to give players the little innovations they want.
So, I guess the real question is, do you want something with proven results? Or do you want to take the chance on a marker that MAY be the next big thing?
A bird in the hand is worth two in the bush.
Just my .02 cents.