Welcome... since you're coming from a storm, you may very be happy with it. Me, I came from a 3Gs, which I am probably going back to. Can't deal with the following:
Typing - No built-in multitouch. i type fast and I tend to almost hit two keys at the same time... on the n1, I couldn't do that. Since it's a storm you have, it probably won't both you.
Accuracy - From what I'm told, it's because of the sensors that HTC uses and isn't as accurate, but from my experience, the droid was the same way. Example... I'm browsing the web and want to click a link that's near several others. On my iPhone, 9/10 times, I'll hit the right link. On my Nexus (and on the Storm), it was more like 5/10, sometimes less.
Copy & Paste - Never thought I used it so much until the iPhone got it and did it the right way. My Pre could only copy editable text, and Android did the same thing (at least that's the case on my N1). Most of the time, it's not editable text I need to copy. On the Pre, my workaround would be to act as though I'm forwarding a message and then choose what I want, but on the N1 (maybe Android in general), I can not do this. I need to use the browser to go to gmail to copy.
Gmail - this actually comes as a shocker. Push is not pushing. I have a couple of friends who have experienced the same. I've been testing it out all week and my iPhone gets the push within 5 seconds. The Gmail app on Android has yet to reach me before 20 seconds. The first day, I was receiving emails within 10 seconds and this was without a sim card inserted. There are no excuses. Should be flawless.
Things I loved/liked about it:
Google Voice - the intergration with the phone is second to none. Being able to choose when dialing out whether you want to use your wireless number or Voice number is one of my favorite features.
Screen - remarkable. No complaints, no even in the system. Less visibility is expected.
Google Apps - Buzz, Tube, Goggles, Gesture Searh, Earth, Translate & Listen. They intergrate well with the device and why shouldn't they, it's by Google for Google.
Browser - crazy fast. NYTimes and others load up as advertised.
Customization - the best. out the box, and probably even after that, customization is second to none.
Widgets - cool. i don't use them much, but they're really cool to have. i am currently using one for sportstap, buzz, tube (altho i'll probably never use), news/weather and word of the day from dictionary.com.