Android 1.5 is just around the corner. It introduces APIs for features such as soft keyboards, home screen widgets, live folders, and speech recognition. While none of this will be available on the T-Mobile G1 (until T-Mobile does an official release – IF they do) it’s worth getting ready for.
Here’s a great writeup on making screen orientation changes faster. I figured out a bit of this myself with when I wrote ConvertDroid, but there are some great tips in here to avoid memory leaks. Worth a read.