Cucumber driver recommendations?

I am on a project which has been writing acceptance tests in Cucumber which drives the application via capybara and celerity. The tests have been getting more and more flaky over time as celerity frequently looses it connection to HTML Unit. I am looking for suggestions on more stable web drivers. We have used Selenium in the past and it also tended to be flaky. My project is using jQuery so a simple HTTP library is won’t work.

I think the more long term solution is to have less full stack UI testing and more Cucumber tests which hit the core business logic in the models. However, I have a set of existing Cucumber tests could be more stable.