I've just been experimenting with InfiniDB and have managed to get it going without too much trouble (following a tip from Joe who has also been having some success with it).
I had been using Infobright a bit lately, as per this thread, and following Joe's comments I thought I'd have a look at InfiniDB, too, to see how they compare. The only other comments I'd seen about InfiniDB on these forums were Michal Klos's experiences The specified item was not found., which made it sound like a non-starter, so I thought I'd just post a few quick notes on what I've found.
I'm using version 2.1 of the InfiniDB community edition, which has just been released. I'm guessing that has just added enough capability to get past the issues reported by Michal. I'm running the Win32 version (because the 64 bit version isn't out yet) on my laptop.
All I have done so far is create and load a single table which I also have in Infobright and convert a copy of the Tableau workbook for Infobright to run against the InfiniDB version.
The table loader for InfiniDB has a pretty clunky interface, but handles data errors much better than JET (which quietly ignores them) or Infobright (which aborts the load on the first error - or even quite often when there arent errors and also lies about where the errors are). It is also seriously fast - InfiniDB loaded my 102 million rows in 16 minutes at the first attempt, and that was with both the input file and the database on my laptop's hard drive. That compares with about 25 minutes for Infobright and quite a long time for the Data Engine (I haven't timed it, but based on past tests it would be a few hours).
The resulting database was significantly larger than with Infobright (18 GB with InfiniDB, 1.1 GB with Infobright). This is because InfiniDB community edition doesn't offer compression, unlike Infobright community edition.
I repointed a workbook from Infobright to InfiniDB by simply changing the MySQL port number to the InfiniDB one. All 20 or so worksheets displayed correctly. Initially there was one error reported on a query to do with displaying quick filters, but this turned out to be because I still had the datasource customisations for MySQL connections needed for Infobright in place. Removing CAP_QUERY_HAVING_REQUIRES_GROUP_BY fixed that.
I haven't done any timed comparisons yet, but my impression is that sheets take quite a lot longer to display with InfiniDB than Infobright. I suspect the lack of compression may just mean there is a lot more data to read from disk - so I expect it might be a completely different story with the enterprise edition.
I'm also fairly sure that both are a lot slower than the data engine for quite a lot of my analysis - particularly where I have calculated dimensions. So there really are pros and cons for all the options at the moment. It will be very interesting to see how the balance shifts with the upcoming Tableau release which various of the Tableau folk have hinted is going to improve some of the Data Engine capabilities in this space.