Most web devs I know use Gravity Forms extensively. This plugin belongs in every web developers toolkit.
After successfully using the Contact Form 7 predecessor to this plugin for about 6 months, we needed a way to do the same thing with Gravity Forms: to pass GF submissions to a third party CRM.
The plugin has processed over 1,000 submissions from 4 different GF forms for us and updated the CRM exactly as mapped. The updates take place within one or two seconds of form submission. We implemented it in two separate multi-site environments and are updating the BNTouch CRM app.
A big plus for me as a developer is that it works with Salesforce too - or whatever CRM the client's using.
Zaus just created a complimentary plugin to 3rd Party Forms that will create and insert a unique Reference ID number before posting to a 3rd party app. This is useful when the 3rd party requires an alpha-numeric ID that is unique across all forms - and all sites in a multi-site scenario. I've used it with Leads 360/Velocify, but can be used with any 3rd party.