Two in my garage: mostly Ryobi, a bit of M12 where compactness matters.
I had Bosch for some while, but grew very frustrated by the lack of tool selection. I think I initially ended up with a few Bosch tools through a Menard's gift card, and that was the best choice available. (Menard's is still dead last in the cordless tool game...)
I gave them to my niece and went all-in on Ryobi about two years ago; all my Ryobi stuff is the newest designs and brushless where that's available, and so far I've been very happy with their performance and value. I have at least a dozen Ryobi cordless tools. Watch the sales at Home Despot for deals, and rummage around in the store occasionally. Sometimes they have a "local" clearance. And, of course, Father's Day is coming up, so there are always some good deals around Father's Day and Christmas.
The one beef I have with the platform is that you really have to pay attention to which tools and batteries are "HP" tools, with extra sets of contacts in the tools and batteries. HP tools will still work with non-HP batteries, but you won't get all the possible beans. (HP batteries, of course, work perfectly well in non-HP tools) Their packaging and descriptions make it unnecessarily difficult to tease out this info.
And like any 18V-ish+ platform, the batteries can be just plain awkward; you have this big heavy box hanging off the tool somewhere. I can't see where one platform is much worse or better in this regard.
I recently added a few Milwaukee M12 tools to the mix, because there's no other platform that has a similar wonderfully compact form factor. I grabbed a great deal on two batteries and a screwdriver for $50 at Home Despot this winter, and quickly added two fantastic M12 LED lights. I'll add more M12 stuff as deals pop up at Northern Tool and HD, but it's not a priority.
