I demoed the Line Prophet 80 last season for 2 days on packed Sierra conditions (at least a week past storm).
I enjoyed them. Nimble, quick, very much similar to the K2 Apache Recon, in my opinion. They held up pretty good on firm hardpack (didnt' have full-blown ice conditions, but it was hardpack) and they were quick and agile in normal cut up semi-soft snow and on the groomers. I was able to open them up pretty well and they were suprisingly turny.
One of the days I demoed them I was riding with two boarders who stay mostly on-piste, so I never took them into the chop or leftover powder, so I can't say how they handle that (perhaps the reason why the new 90 is popular...I don't think they had the 90 last season, only the 80 and 100 and 130, if i'm correct).
The only thing i heard negative about the skis is that they had some either edge or delam problems early on (most of the shipments from last season didn't get into the shops until late Dec/early Jan).
I almost plunked down on a pair, but once I found out they were made in China, I began searching for European options (ended up with the Karma, which isn't quite as nimble as the Line, but it's also stiffer and a bit wider. I also ended up with an AK No Ka Oi and a Blizzard Titan 8, both of which are 78 and 80 in the waist, respectively and both are also considerably stiffer than the Prophet).
Overall, though, I enjoyed the ski and almost bought a pair over the summer, but found the Blizzards for cheaper.
The only caveat I'll ad is that I wouldn't consider the Prophet 80 to be a park ski. Even Line lists it on their Big Mountain section on their site. I don't recall it being terribly twin tipped, either (more like a Mantra in that the tip is raised and rounded, but more in-between a standard square tail and a true twin).