As an xTuple Development Partner I'm biased, but you might want to add openERP to your list. I would suggest you simply web search for the reviews - where you can be a better judge of the reviewer's independence.

Here's a link for ratings and reviews on PostBooks the xTuple open source edition:
http://sourceforge.net/projects/postbooks/

OpenSurge is going to be presenting at the Accounting Software Expo in Atlanta, GA on May 20th. xTuple ERP is the only open source ERP solution being presented at this conference.

There's more information about the Expo and open source xTuple ERP on our website.

http://www.opensurgegroup.com/index.html

Sharoon Thomas

Posted on April 13, 2010

Yes,

You should consider Tryton too in the list of reviews.

Tryton is a three-tiers high-level general purpose application platform under the license GPL-3 written in Python and using PostgreSQL as database engine.
It is the core base of a complete business solution providing modularity, scalability and security.

Tryton Website: http://www.tryton.org

Sharoon Thomas
http://openlabs.co.in

Dan

Posted on April 14, 2010

I think you should also consider ERP5 which is a major Open Source ERP. To know more about all the solutions, you can go and see Ubuntu website.

Pathik Shah

Director, P C Shah & Associates

Posted on May 16, 2010

I think you should have a look at the following links. It doesn't give you straight away comparison of all the products you mentioned but with some manual tuning you should be able to arrive at the conclusion:
1. http://www.sourcio.com/blog.2005-12-08.3811378908/blogentry.2006-03-28.124394...
2. http://www.erpsoftware360.com/erp-open-source.htm
3. http://blog.taragana.com/index.php/archive/top-5-open-source-enterprise-resou...
4. http://opensourceerpguru.com/2008/01/08/10-evaluation-criteria-for-open-sourc... (Its about evaluation criteria while selecting opensource erp)

Eric Kimberling

President, Panorama Consulting Group

Posted on Aug. 4, 2010

Chris,

I am coming into this response a bit late, but for you and others reading this question I'd point you to our online ERP database that offers customer reviews based on a variety of criteria. Open source software is included in this database and xTuple has a current ranking of 8.8 out of 10. This is fourth highest rating of all ERP vendors thus far, which says a lot for this open source provider.

The link for the ERP reviews is: http://panorama-consulting.com/resource-center/erp-database/erp-vendor-ratings/

Eric

Fred Blauer

CEO,CFO,VP,Director, Fred Blauer and Associates

Posted on Oct. 24, 2011

I'd really suggest a good needs analysis as a starting point, since there is no one solution that is best for everyone. It really depends on a lot of factors such as required features, size of company, industry, localization, and a lot of other considerations. Having said all that I am maintaining a blog on the subject of open source and cloud based accounting and ERP software here:
http://openacct.wordpress.com/