I found the following digested case from A. Benjamin Spencer’s Federal Civil Practice Blog.  It may be a month old, but nonetheless timely!  Professor A. Benjamin Spencer is currently a Visiting Professor of Law at Washington & Lee and an Associate Professor at the University of Richmond.

E.D. Kentucky Holds Defendant Failed to Make a Showing Plain Legal Prejudice; Grants Plaintiff’s Motion for Voluntary Dismissal
Per Gunn v. American Memorial Life Ins. Co., Slip Copy, 2007 WL 2000036 (W.D.Ky. Jul 03, 2007) (NO. CIV A 307-CV-181-S):

Under Fed. R. Civ. Proc. 41(a), a plaintiff may file a motion to voluntarily dismiss his case. Pursuant to Grover by Grover v. Eli Lilly & Co., 33 F.3d 716 (6th Cir.1994), such a motion should only be denied where a defendant can show plain legal prejudice flowing from the dismissal. Id. at 718. "In determining whether a defendant will suffer plain legal prejudice, a court should consider such factors as the defendant’s effort and expense of preparation for trial, excessive delay and lack of diligence on the part of the plaintiff in prosecuting the action, insufficient explanation for the need to take a dismissal, and whether a motion for summary judgment has been filed by the defendant." Id. Given that a dismissal under Fed. R. Civ. Proc. 41(a) is one without prejudice, these factors take into consideration the time, effort, and money defendants have spent in preparing for trial.

Defendant primarily argues that the court must deny Plaintiffs’ motion for voluntary dismissal, and enjoin Young [a nearly identical pending class action complaint against the Defendant], because Young "threatens to frustrate proceedings and disrupt the orderly resolution" of the case at hand given that Congress expressly provided this court with jurisdiction over Gunn through the Class Action Fairness Act of 2005. 28 U.S.C. § 1332(d). The court finds no merit in this argument. The standard for granting a motion for voluntary dismissal does not consider whether the court maintains jurisdiction over the case in question. It only considers whether a defendant will suffer plain legal prejudice from a dismissal, which as explained above, is normally limited to considerations of time, effort, and money. As explained in more detail below, it appears that courts have only deviated from this standard in instances where dismissal would lead to abuse or frustration of the judicial system.

Defendant fails to make a showing of plain legal prejudice. It does not argue excessive cost or effort expended in the case at hand; it does not assert inaction on the part of Plaintiffs; it does not contend that Plaintiffs provide an insufficient explanation for dismissal; and it has not filed a motion for summary judgment. Moreover, those cases cited by Defendant as supporting the contention that dismissal would result in abuse or frustration of the judicial system are distinguishable from this instant action.

. . .

Because Defendant has not shown that it will suffer any plain legal prejudice from dismissal or that dismissal will result in abuse or frustration of the judicial system, Plaintiffs’ motion for voluntary dismissal will be granted.