Easy to use, the right size for my company, and the right price.
We send out highly targeted emails to many small lists and it makes it easy for me to send the email at the same time, but still to all these lists so I can compare response rates of each list. I can then further customize my emails to each list if I want to.
I also like the way it is easy to score, build workflows, and integrate my other campaigns with it.
Probably best of all, it comes at the right price for smaller companies that need sophisticated marketing automation without having to spend a lot of money.
My only peeve is that the import list feature comes with fixed columns. This has limited my ability to export more complete information (such as revenue, employee size, etc.) to Salesforce.com when the lead is ready to be exported.
Maybe there is a workaround I don't yet know about.
I do use Eloqua and Marketo for some clients, but I still think that LeadFormix is the best marketing automation tool that gives a wide range of functionalists out of the box without a great deal of development and customization.
Also for the functionality that I use, it offers the best price/performance ratio