Black & Decker used be one of the most respected names in the tool business back in the 50's and 60's along with Skil. Both started producing junk tools in the 80's and Black and Decker has since expanded their product line into kitchen wares, lawn and garden equipment, portable cordless vaccuum cleaners and other products. Black and Decker's professional line of tools are marketed under the name "DeWalt".
But, it's not reasonable to say that you should only buy professional grade tools. If your idea of a major DIY project is mounting a hose reel to the side of your house, then you would probably do just fine with Black & Decker cordless tools. If you intend to get more involved in home renovations, then you'd be better off going with a professional grade of tool like DeWalt, Makita, Porter Cable, Bosch, Milwaukee, and the newcomer, Rigid, which are the most common of the higher quality names. There's also Sears Craftsman, Ryobi, Hitachi and Panasonic, which are good quality, but less common. (I would rate Hitachi and Panasonic above Ryobi and Craftsman.) And, there is also Black & Decker and Skil that aren't really marketed to professionals or serious DIY'ers. They're more for the person who needs to have a drill to drill the odd hole, but isn't going to do any serious renovating in his house.
Perhaps the best of both worlds would be to check out the 18 volt cordless DeWalt tools at Home Depot and see if they use the same battery pack as your trimmer/blower. If they do, then DeWalt is a quality professional grade tool.
If they don't, then, believe it or not, it might be a good idea to stick with Black & Decker even if you intend to do some serious renovating down the line. The reason why I say that is that is that people new to DIY work will be harder on their tools than the experienced people who have already learned that you can ruin a tool's motor with too much dust or by overheating the tool and things like that. If you're just starting out into DIY work, but intend to continue along that path, it might be better to learn on less expensive tools than on more expensive and better quality ones.
Also, you should be aware that battery packs for the higher voltage cordless tools, like 18 volt and 24 volt, simply don't last as long as the battery packs for 9.6, 12, and 14.4 volt tools. And, I don't think anyone knows why. So, you might as well look in your phone book under "Batteries" and find a local battery distributor that also rebuilds battery packs for tools. A rebuilt battery pack is just as reliable as a new factory part, but will cost half as much or less. And, you can have your battery pack rebuilt with higher rated mAh (milli Amp hour) cells. Those cells will still be 1.2 volts each and you need 15 of them connected in series in your battery pack to get 18 volts. However, the higher the mAh rating on the cells, the more energy you can store in each cell, so the longer the tool will operate on each charge. For example, rebuilding your battery pack with 1700 mAh cells instead of the typical 1300 mAh cells will give you 17/13 or about 30 percent more working time per full charge.