I was just thinking that we've gotten away from the OP's original question, which was about apps that are surprising in a good way or bad. Most people are posting apps which they like (which is totally fine), but how about getting back to the original premise?
Here are some apps that surprised me in a GOOD way:
1. DigiClock, by Dave Goemans: I thought this simple clock widget would just be temporary, but I've found it to be the best combination of looks (some neat fonts, especially with the beta version), size, and versatility. I've found other clock widgets don't have neat fonts, or don't display the date to my liking, or are just too huge in display size and file size.
2. Google+: Really cool UI, a lot smoother and faster than Facebook. We just need to get more people on Google+!
3. Medscape: I didn't expect this free medical database/calculator to be the best overall comprehensive program for patient management in the hospital. Can't beat free!
4. Yahoo Sportacular: I had ESPN Scorecenter for a while, but was always a little annoyed at the relatively sluggish startup. Yahoo Sportacular (who woulda thought that Yahoo could make decent apps?) is much faster, and also leaner. Of course, it doesn't come with ESPN videos, but I never looked at those anyway.
Here are some that surprised me in a BAD way:
1. Chrome: I noticed significant sluggishness, even after it exited beta. And not just on my Maxx--it totally slowed down my Acer A500. I still think the stock ICS browser does a lot of what Chrome boasts (e.g., sync your bookmarks with your Google account, browse Incognito, multiple tab browsing), and it seems to work faster than Chrome as well, at least in my experience.
2. Facebook: Not a surprise in that a lot of people seem to complain about it, but a surprise to me that such a huge social networking company can't quite get their Android app to work as smoothly and as quickly as I'd expect.
3. Google Currents: I tried this a few months ago, and it takes up massive memory. I like Pulse a lot better--it's leaner, but still has good access to a lot of news and blog sites.
That's what I can think of so far.