Any difference in gens?

I had a gen 1 WSM for 18 years, and just replaced it with the newest model.

Has anybody gone through this, and if so, are there any noticeable changes in operation/temp/cooking, etc?

I think main difference is they changed the water pan to hold more water. Some people don't like it because it doesn't leave as much room for charcoal.
The differences in features and capacities are listed in this article I wrote in 2009:

Then in 2014 they added the silicone grommet.

So in terms of cooking, it's really about the large water pan capacity, if you're using water. As Dustin says, it hangs too low for many people's preference, so you might continue using your old water pan if you still have it, or switch to this pan which is a pretty good fit:

I'm also looking at other options for alternative pans, so stay tuned.
Thermometer, different door, larger water pan, heat shield on bottom, heavier duty legs. I still have the original but have cooked on newer ones. I didn't notice any difference with the cooks once they were broken in.
I have a 2004 or 2006 model 18" wsm and a 2015 that has the door lever-bigger water pan- therm in the lid and heat shield. Both cook identical, I went through the process of making sure the sections are as round as possible so the sections don't have any air leakage. I have no use for the bigger water pan, the heat shield kept fall off so I took it off and use the shield covered in foil in place of the water pan to block direct heat and catch drippings. This may be nostalgia talking but I think I prefer the older version, not sure if weber has issues with the new handle material but I have a jumbo joe and the newer wsm both of which the handles keep coming loose . The joe lid handle is now stripped and need to get it replaced
Latest models are:

14.5": 711001
18.5": 721001
22.5": 731001

No changes to any of these grills since 2014. No changes planned for 2020 as far as we know.
Thanks Chris.

We moved and I got rid of my ancient Weber smoker and kettle. Now I need to re-load.

Got rid of :confused: you should have just refurbished lol. We got a free 90's kettle that i spend a couple hours scraping out and washing down. Threw some new grates in it and it's as good as new. To be honest i'd have kept the charcoal grate that it came with too if the old owners hadn't had it so gunked up. The one i started with too was probably a worst case scenario grill. I'm actually keeping my eye out for freebies to fix and sell.
Great point.

I should have mentioned that over the years I had scraped it, washed it and put replacement parts in where needed. Didn't want to move it because I have new grill fever.