The most useful feature of Vialb for me was being able to have all my interactions organized into different projects so I could see where each prospect stood at any given point as well as who had already responded or not yet replied.
We were also using Salesforce but found this system gave us better visibility over our leads/prospect info which made life easier overall! There wasn't anything i disliked about viaBl other than maybe having too many features sometimes (and needing some training). Definitely try them if they're available near by - we used their demo account prior to signing contract wtih full implementation services from another vendor whom unfortunately did nothing right after going live :(.