We use an app called Distribution Engine to assign Tasks in Salesforce via Round Robin. Marketo assigns the Task to a generic user and then the Distribution Engine app reassigns. Works great!
Brian, Were you able to assign leads based on lead score. So if I have 2 sales reps can I create logic that splits the high quality leads between reps?
Bethanie, sorry just seeing this comment. Yes, we assign leads based on lead score. Marketo doesn't change the Lead Status to "Marketing Qualified", and create the task, unless the lead score meets a certain threshold. Once Marketo changes the status and creates the task, we use Distribution Engine to assign the owner via round robin.
A client of mine used a default "user" to assign all leads to him from Marketo - it worked exactly as you described, all new leads pooled in and sales reps could follow up on the next one as soon as they were ready.
I see one problem with this approach - the dummy user can't really be "reminded" to follow up on a lead using auto reminders, pop-ups or emails. When it's just a pool of leads and nobody really owns it, things start to fall through the cracks.