We're only using one single position right now, a custom size, delivering about 135k impressions a day (all told the site has many positions that require an aggregate total of over a million ad impressions a day), and I'm noticing that delivery is not always smooth. Sometimes I get broken ads, sometimes the space is empty. This is not a user error, it is definitely an unreliable ad delivery situation.
What's worse, is that the stats system is constantly failing to load, with dreaded server errors. In the past 3 days I've been trying to access stats with only 10% of my attempts working. This from a company set to expand to Japan today? Their support forums have users who are complaining about problems with no one responding.
Truly I want OpenX to succeed, the PhpAds platform it evolved from has been in use for over a decade on many sites, including some of my own. However, right now the service has left alot to be desired in terms of reliability - I can't get stats to work on a measly 135k impressions a day, what happens if I need to deliver a million, or 2 million impressions a day? Doubleclick for publishers is EASILY handling this volume right now with no problems for me.
Has anyone else got some positive things to say about the OpenX hosted solution?