Saleslogix (SLGX) was a Salesforce competitor which went public during my tenure but ran out of cash in 2001.  I worked on SLGX for a year and then was promoted to team lead and architect for SupportLogix.

We'd purchased a small call center company to merge that product with SLGX as a companion offering.  The codebases  were vastly different, however.  SLGX was quite sophisticated as it's really a CRM platform with a SQL engine supporting several RDBMs, a form designer and its own VBA-ish scripting language.  By contrast, the call center app was kindergarten-level code using a fully normalized database versus SLGX's denormalized one.

So it was a nightmare project.  But we finished it in nine months and ten months later it paid for itself and was making money.  It's a success that I rarely think about these days.  SLGX is the most sophisticated software I've ever worked on.  It was written in Object Pascal (Delphi) and had extremely high customization ability.   Most of our customers were small IT companies who customized and resold SLGX to their customers.

This was my first commercial software and it's surprising it's still in use.  It was written for a pre-phone world and did database synchronization over a modem.