From an SEO standpoint, its not the best idea, but if the trade-off is a highly enhanced user experience then it can be worth it.
As far as SEO goes, its a roll of the dice as to whether that content is both crawled and considered as part of the main text of the page (i.e. whether or not it gets calculated into the ranking algo for the page). So even with the content crawled it is not necessarily going to contribute to the "on page" text as it relates to ranking signals.
Google has not provided much clarification as to "how" they make this determination other than by means of a manual review (which in reality most sites don't get...or get every once in a blue moon).
Across our managed network over over 15,000 sites we haven't yet been able to find any clear cut evidence that is a smoking gun in either direction. As of now, it appears to follow much of the same random logic as JavaScript on page as it relates to Goog's crawlers...meaning that it sometimes IS and sometimes ISN'T readable by spiders.
Regards,