I like the stock android calendar (on the droid1). That being said, calengoo does seem pretty slick. In beta. Current version expires January 14.
Don't want to root this phone.
Looking forward to seeing the new incredible HD (Thunderbolt). Being HTC I'm thinking it will have the same calendar issue.
FOUND A SOLUTION!!!
It's kind of funny, I read this thread several days ago when I bought my new HTC Thunderbolt, and I shared your frustration, Eurosteve. Those who have responded to your post don't seem to understand the issue at all. I hate this HTC calendar, with the 7-day view that doesn't show the text.
But it is possible, without rooting. It was fairly simple to accomplish, I just backed up the APK from my old rooted Droid using a nifty app called Super Manager, transferred it to the SD card of my new phone and then installed it onto my TB. Super Manager requires root, but since I've extracted the necessary APK file (app installation file), you shouldn't need to root your phone. Just download the APK that I'm attaching to this post, install and you will have your trusty old calendar.
I've found one quirk so far: when you open the Calendars menu (to choose which calendars to sync and display), you will probably get a force close. Don't worry, just switch over to the HTC Calendar app and select the calendars; it will instantly update on the stock calendar app. That is a minor inconvenience for me, to be able to use my trusted Droid calendar. I love the Thunderbolt, but I absolutely abhor everything about the HTC Sense UI.
Hope this helps! Please post if this method is successful for anybody, or if there are any issues.