Basically just off - intermittent - low - high. I haven't found reason to complain about it really. A more important upgrade is to swap out the crappy stock wiper blade for an Icron Ranger.
I changed the wiper relay on my Lotus Esprit for one with built in electronics that gives you an intermittent function - its just a case of swapping the relay. Someone here has done it for an Elise so its probably possible on the Roadster but not tried it yet. JnC's Programmable Intermittent Wiper Relay Hack - LotusTalk - The Lotus Cars Community
Yep, not adjustable on any. It's the Lotus Elise stalk - just delay, low, and high. You can nudge it up for a single wipe.