Based on how other apps behave-I can't blame them for not releasing apps.
Slow. Forever to load (native or not). I literally only use the remote for my Hue lights and some of the inbuilt apps (music remote). Dark sky complications is good. I could take my iPhone out of my pocket/bag ten times in the time it takes some apps to kick in.
Having said that-I still like my watch. I have reconciled myself with the fact it'll probably never be more then a nice time keeper, average remote control and decent notifier.
I think this is very dependent on the app. I've used some native watch apps that are worse (slower, crash, freeze, etc) than when they were non-native. However, I have seen four apps in particular that make me think it's all in how the developer writes them. These 4 native apps run flawlessly in my experience and open very quickly (within about 2 seconds) on my 42mm SS.
These are:
OmniFocus - probably the fastest I've seen... Even faster than it's iPhone counterpart actually, complication works flawlessly
Carrot Weather - Also very fast to open and runs smoothly, great complication... probably my favourite at the moment
DataMan - Also works very quickly and flawlessly although I find the complication kind of useless
Fantastical - Again very quick to open though not as quick as the three above. Complication is better than the stock apple solution but I expected more from Fantastical for their watch face complication.
Some I've found that are absolutely terrible are:
The Weather Network - Crashes on start, complication never works
The Weather Channel - Same as weather network
App in the Air - loading this app onto my watch results in the same problems as the two above however with one very interesting side effect. If the app is installed on my watch, the iPhone app will NEVER launch, it just crashes. If i remove the watch app from my watch the iPhone app begins working again. I don't know how these are related but it's something I noticed and thought was funny.
One thing about these two groups... The good apps are all paid and the crappy ones are all free. I guess with Apple Watch apps you really do get what you pay for.