It's hard to get excited about software for lawyers, and I think that's why Disco has flown under the radar a bit, but I think these guys are going to be huge. They've made exponential improvements in e-discovery software.
And they are missing a huge piece--predictive coding and advanced analytics (email threading and near-dup are EXTREMELY common). If you are in NLP, ML and/or IR, the legal industry is probably one of the most exciting places to be. Huge datasets, available annotators and tons of money. It's a red-hot lab of state of the art techniques being tried in the real world instead of on the Reuters, 20-newsgroups, Enron, and other "canned" datasets.
One concern that I have is this "Secure Infrastructure--no installation required". This suggests the cloud. The other is "Upload your data by FTP".
Think about e-discovery for a moment. The toxic material stored is pretty much a superset of all known toxic material--PCI, PII, HIPA, and so on. Many customers require physical control of where this information goes. Zero installation means that it is not a server under your control.
There are many pieces to the EDRM process (http://www.edrm.net/resources/edrm-stages-explained) and it is not clear that DISCO covers all of them. 'tucros3141 in a parallel comment mentions some of them.