My home regional is this Saturday and I don't know what list I'm taking. I thought I knew, but then I lost three games in a row with the list I thought I would take. Perhaps the force will guide me...
Even a loss is practice. I'd recommend taking a look at what caused the losses and try to determine if they were preventable. If you find they were not (example: too much trust in dice, not enough mod options), then the list is likely going to suffer in a competitive atmosphere. If you think they were preventable (example: setup mistakes, position miscalculation), I'd consider those losses as valuable play time that will benefit you at a Regional.
Generally, the person with the most experience with their list is going to be the winner more often than not. Who else do you expect to actually trump their hard counters?
I played a Deci/Ace list designed to destroy a Vassal opponent (I'd researched their previous matches), but it had been awhile since I'd flown a Deci -- my opponent managed to limp away with a victory despite all odds against him, and it was because he'd been practicing the list (and, you know, being a solid player otherwise helps!).