I posted here a few times about a problem I was having deleting text messages once the thread got to 50 or above. When I went to the Sprint Store a representative that had my phone recommended that I do a hard reset, I was a little concerned at first but after realizing my contacts were going to be available through my gmail contacts and all of my apps were going to be saved in Android Market I decided I'd go through with it.
I had 2 threads with a combined 6,000 texts and there was NO way the phone was going to be able to delete them in a timely manner or without freezing my phone. I went through the steps for a hard reset and it was surprisingly simple. It probably took a total of 5 minutes to do the reset and once I set up my gmail all of my contacts were restored. Redoing all of my apps/settings really wasn't as difficult or time consuming as I thought and now my phone runs remarkably faster. If you have some apps you'd like to completely get rid of, texts you'd like gone, or just want to see the snappy response back in your phone I really recommend doing a hard reset. It took a total of 20 minutes to get my phone running back (with apps etc) how it was before the reset WITHOUT any of the lag or extra texts.
I also think it had a slightly positive effect on my battery life, but not completely sure because it's only been one day. A possibility for those of us who are having battery life issues and feel like theres nothing left to try. I think deleting COMPLETELY all of the apps you don't need/want and clearing everything just helps the phone in general.
This being said I'm STILL waiting for the 2.1 update and really want to see how it improves my performance as I'm not looking to completely reset my phone once a month or something.