There are many different types of Paid Search agencies. Some rely on the engine's UI and spreadsheets to do their work, the more sophisticated have either built or rented a tool set to use for bidding, ad management, etc. Some in this last category expose their UI to their clients, while others, like RKG, use their proprietary tools on behalf of their clients.
The tool providers call around and offer tours of their products and I usually take them up on it...once. It's always interesting to see where others are in the evolution of the industry. Most of these tools do the basics very well and would be a huge help to an agency just wading into the space.
That said, on the all important analytic front the best of these systems is about where RKG was in 2005 -- not bad, but nowhere near where we are today. Sometimes they ask: "what would RKG need to see in this tool that would make you seriously consider switching?" "A reflection of my corpse." is my honest, but not so helpful response.
Without going into the underlying statistics, the data architecture, methodology and other important differences the biggest weakness is perhaps in the limitations of the UI. I'm not talking about specific features that are missing, I'm talking the limitations inherent in any UI.
I'll show you a screen shot of the most powerful piece of RKG's UI:
Yep, it's just a blank query window. In that nothingness, our analysts have the flexibility to find and do anything and everything. The power to custom-craft any data, any analysis, any bidding enhancement to fit just the ads and data you intend cannot be hard-coded into a UI.
The drawback to infinite flexibility and that power that comes with it is that we can't expose our UI to our clients, and we have to hire remarkably sharp people who can learn to be power SQL users and train them. We've had to grow slowly relative to others -- still 315 on the Inc 500 list, but -- and only recently moved from having one full-time sales person to having 2.5 FTEs on Marketing/Sales/PR.
We think the benefits far outweigh these inconveniences. As I've argued before, you can't lead in this space if you're using the same core technology as others; the ability to add features and tools as needed is irreplaceable, and the power and flexibility gained by having thoroughly trained sharp analysts with the power to code anything they need into the system cannot be supplanted.
It is easier to follow a different path, but we think we've found the right one for our firm.