Obviously an 18 year felony is much more serious but I wonder how tech companies view misdemeanors such as DUI, Possession of Marijuana, Domestic Battery, etc?

Tech companies in the bay area would probably wonder WTF you got arrested for marijuana or other minor drug offenses.

DUI I think would be a more serious issue, depending on the area. In the Bay Area, DUIs are pretty frowned upon, since there are other transportation options. I think they're much more accepted in rural areas.

I know plenty of tech people who have convictions for assault (bar fights), drugs, computer crime (particularly as kids), etc.

I wonder if tech companies in general would be more tolerant since they tend to have more laid back cultures compared to corporate environments.