Most of mine are Ryobi. They're cheap and it's nice being able to power any of them with the same battery. I've slowly been expanding my collection over the last 7 years or so, and I'm yet to have a problem with them. They don't get used daily, but see their fair share of abuse. Only recently did I wear out the first battery, and it's one of the ones that came with my 7 yr old dill/impact combo. All the others hold a good charge, and power remains consistent till the end. Any time I'm at Home Depot, I look for the 4ah battery 2 pack for $99. For how long those batteries hold a charge, you can't beat the price. I especially like the 3spd 1/2 inch impact; it'll take off lug nuts that would give a gorilla with a breaker bar a run for it's money.
If I depended on the tools to put food on the table, I'd probably go with a bit better brand. Since I don't, Ryobi works good enough.