I haven't had problems with apps loading slowly for a few updates now. Am I just lucky, patient, or am I using better apps? The ones I use the most, and usually access from complications, are Fantastical calendar and Carrot Weather. Both load and update very quickly for me. I even have Fantastical loading three Google calendars and one Office 365 calendar. It is absolutely faster and easier for me to check my calendar or the weather on my watch... especially if my iPhone is zipped up in a jacket pocket or bag/backpack. Yes I encountered long app loading times and crashes back before OS 2, but each update has improved performance. Not all apps are created equal though, so I have replaced a few slow apps with faster ones.
I will say that I don't go to the app screen that often. I disagree with the statements that apps are useless, or that Apple should not have allowed them for the first version of the watch. The ability to run apps was a huge part of the appeal for me, but I don't need that many. I probably use half a dozen regularly and another half dozen on occasion. I use a grocery app (Bring) that I launch from the app screen. I also use Cloud Outliner quite often. I create lists or notes in outline form on my iPhone and then navigate them easily from the watch. Sometimes I load an app that shows me the tides in our area. I can control our Philips Hue lights from my watch as well.
Many of my third party apps are not ones I open directly on the watch, but only launch or interact with when I get a notification (Due reminder app, Slack, Yammer) or when I use Siri (Yelp, setting a reminder that will be added to Due, etc.).
It's really best not to have too many apps cluttering up the app screen, or too many glances to swipe through. If I'm not going to need an app on the watch for awhile (like a travel app), I will either move it away from my core apps or just remove it from the watch until it is needed again.
Sean