Well I have successfully upgraded to version 1.9 of dasBlog. I didn't have any problems. For anyone that is interested, the process of upgrading from 1.8 to 1.9 is very straightforward. According to the Scott Hanselman's upgrade note, you should be able to merge any of your own changes into the web.config, backup any custom themes, and overwrite most of the other files.
The process I followed was as follows:
1. merged my changes into the web.config
2. merged my changes and settings into the appropriate files in the SiteConfig subdirectory.
3. I left my content directory and my logs directory alone but copied over everything else as though it were a new install.
4. Once I had everything copied, I browsed to the site, logged in, and changed the administrator password (since in 1.9 it is encrypted and thus it is probably not advisable to change it directly in the config file).
There you have it. Pretty simple. I had no problems and am looking forward to utilizing some of the new features. Oh and BTW, I am posting this entry from Live Writer so there are no issues with Live Writer and 1.9!