Took me a couple of days to warm to the GUI, but I now prefer it, as it is much quicker than the FSX one (such as when changing aircraft - as there is no main menu as such).
Anyway, no framerate issues at all and I tested it with time accelerated up to 64x and had no issues whatsoever.
I have installed a few freeware add-ons and quite a few payware. It was only after installing and testing for 3 days that I came across the first payware prog that refused to install (error - could not confirm FSX version) and then I used the infamous registry tool and changed the path to my P3D one and it went just fine.
All of the add-ons have worked flawlessly (I did have to purchase an extra licence to use REXE Plus in P3D, but it's only about £3). Most stuff goes in when you point the installer to P3D with the "Browse..." button (I did copy all the FS exe files to the root P3D folder in anticipation of those progs that look for it).
The things I was a little concerned about - firstly the GUI, but as I said, I warmed to it very quickly. Secondly was the lack of AI aircraft. There were plenty of them on the ground, but not a single one flying. P3D uses the default FSX aircraft as AI - so you get all the standard MSFS fictional airlines at your airports. I tried to install UT2, but every single time I try and do that - to FSX or P3D - it messes me about something chronic. So for the first time in years, I installed TrafficX and the Military pluspak and it works very well.
I'm also not convinced about the scenery. I haven't used default FSX for so long, that the P3D scenery might be just the same - but it was pretty awful, so I installed my faves (UTX and GEX) again, without issue. That works fine, but you can actually see where the scenery detail is 'filling in' a few miles in front of your aircraft. That's a bit naff, to be honest, but it may just require some settings tweaking - so I'm giving it the benefit of the doubt.
Why a dev licence? Well, firstly because the "all changing" version 2 is mooted to be close to release and buyers of v1 will have to buy a new licence. The dev licence allows you to pay $9.95 per month - and stop or miss any month you like. So if you don't like it, or aren't going to fly for a while you can simply miss a month or two, or stop paying completely.
Also, I'm hoping that the Flight1 scenery editing progs will work with it - I had fun with them in FSX, but I'd like to do some more serious stuff in P3D - such as model some local strips. I also want to see how my homebrew paint jobs look - which comes under the "Dev Network" criteria. When v2 comes out, if I really like it, I'll probably buy a full licence straight out.
What is working so far from FSX? This:
French Airports
Papua New Guinea Bush Flying
All Capt Sim so far
All SymFlyer gauges
All alphasim so far
FSX Enhanced Autogen (AVSIM)
All Just Flight so far
UTX Europe
A2A aircraft (AccuFeel went straight in - Shockwave3D Lights doesn't - has to be copied over from FSX)
GEX Europe
All Iris products
REXE Plus
MilViz T-38
All freeware airfields
All Wilco so far
All freeware aircraft so far
and so on. PMDG have stressed that their licence doesn't cover use in P3D so I'm not going to say that I installed the Jetstream JS4100 or that it works perfectly.
I have quite a bit of stuff (I don't use FTX/OrbX as it has given me nothing but problems in FSX, though I may try it in P3D if/when I can afford FTX global) so if there is anything in particular that someone would like tesing in P3D - give me a shout and I'll test it if I have it. I've not yet tested DaveM's classics, but their turn will come shortly and I see no reason why they wouldn't work. In the meantime, if I come across something that definitely doesn't work, I'll be sure to mention it.
So, for me, so far it's a
PS - forgot to mention; I have both FSX and P3D installed side by side on the same hard drive, working just fine.
