The Toro cordless trimmer has plenty of power--even after 45 minutes of use. I also own the Black & Decker 18 volt cordless trimmer with 2 removable batteries. The Black and Decker loses its power in less than 20 minutes--sometimes 15.
I store the Toro unplugged, and it holds its charge for over 6 weeks. Try that with the Black & Decker 18 volt cordless trimmer. The Black and Decker loses most of its power in less than 2 weeks.
The Toro doesn't always win over the Black & Decker, however. The B&D is superior for trimming grass along a sidewalk. It's also more ergonomic and weighs much less. I do, however, get tired of replacing the batteries every 15 minutes and having to recharge 2 batteries after every use.
Overall, the Toro is a great value for the money. It is a little heavy, but that's due to the large battery. If you have extremely light trimming to do, especially along a sidewalk, definitely get the Black & Decker 18 volt cordless trimmer. If you have lots of trimming to do and can deal with the extra weight, definitely get the Toro. It runs longer, stronger, and, depending on how long you use it, you don't have to recharge it after every use.