We do themes semi frequently enough to have a sort of process down. Never any problems here really. We just opt to not use much of the Wordpress ui helpers and make sure we’re not using plugins that generate their own ui. Then again they mostly end up being hosted with Wordpress VIP and they hold everything to a fairly high standard.

I’ll admit though, it’s a bit weird having a prod and dev environment with how many tweaks Wordpress can have. Haven’t really come up with a good solution for that.