Very few viewer/reader applications support JPX, and the few that do typically only support a limited subset of JPX's features. Applications often don't state which specific features are/are not supported.
Viewing of files that use any of JPX's advanced features (fragmented codestreams, composites, advanced colour support) may turn out to be problematic in the future because of a lack of readers that support these features. This was already addressed by Goethals (2005), and the situation has become more poignant with Adobe's decision to discontinue JPEG 2000 (incl. JPX) support in recent versions of Photoshop Elements.
Jpylyzer can be used to check if a JPEG 2000 file contains features that are not part of JP2. A limitation is that jpylyzer is not able to give any detailed information, for the simple reason that is does not (and will not) support the JPX feature set.
Avoid JPX whenever possible and use JP2 instead (see also the Recommendations in Section 2 in Buckley & Tanner, 2009). For typical archiving purposes, the only real advantage offered by JPX (over JP2) is its extended colour space support (CMYK spaces + support of N-component lookuptable-based ICC profiles). With hardly any readers being available to handle these features, one should consider not using JPEG 2000 for such cases altogether.
Goethals, A. Action Plan Background: JPX. Florida Digital Archive, 2005. Link: http://fclaweb.fcla.edu/uploads/Lydia%20Motyka/FDA_documentation/Action_Plans/jpx_bg.pdf
Buckley, R. & Tanner, S. JPEG 2000 as a Preservation and Access Format for the Wellcome Trust Digital Library. King’s Digital Consultancy Services, 2009. Link:http://library.wellcome.ac.uk/content/documents/22082/JPEG2000-preservation-format