Dear Miss Snark,
A year ago, I met an editor at a writer's conference who invited me to submit the entire manuscript of my novel. A few months later, I hired an agent, who was brand-new. I let the agent contact the editor, which she did.
The editor ultimately rejected the novel with the very kind words, "I will be actively looking for whatever this author writes next."
Soon after that, the agent stopped sending out the manuscript and gave up on it, so I politely severed our business arrangement.
I am going to another writer's conference in a few months, and will be pitching a brand-new, shiny manuscript to the same editor who almost liked my work before. If the editor says, "Didn't you have an agent before?" What do I say? I don't want to sound fickle, nor do I want to sound like an idiot for getting mixed up with such a lousy agent.
You say "my agent and I have parted company amicably". The word lousy never enters your mind let alone your conversation. And don't worry, she's not going to ask, and she's probably not going to remember you unless you mention it first.
And you don't "hire" an agent. If such a state of affairs should come to pass, I know you'll be glad to offer an hourly rate commensurate with my value.