I currently use beta 1.0 for one of my tools and it has been functioning for years without a problem. I think they are just saying don't sue us if you use in production and didn't pay for it :-)
It is way cool. I've been an enterprise user for some time now and am excited to get to use it on other projects for which there wasn't cost justification in the past.
While I am an enterprise user of memSQL now, I still have a machine running the beta version 1.0 from years back. It is still stable and still fast as hell.
I have been an enterprise user and had the luxury of using the 4 beta for the last month or so. I run a cluster of 18 machines with 192 cores and 540GB of RAM.
Impressions:
memSQL is remarkably stable. I actually have one machine running the old memSQL 1.0 beta that has not rebooted in months. 4.0 has similarly stable. The only problems happen when you run too many other processes on the aggregators (which is really just me being stupid).
Speed is great and the wire compliance with mySQL makes it very easy to develop for. To be honest, the "keeping the data in memory" part isn't the best part, it is the query compiling. It is incredibly fast. Often a query that takes 30sec to 1min to execute will compile down to fractions of a second. It is very cool to watch and never gets old.
We are looking to literally move all of our internal stuff to memSQL community edition while keeping our customer tools on enterprise.
One option would be to "avow" links rather than "disavow". Start with the assumption that all links are valueless and untrustworthy and only count those which the webmaster has marked as good.