You can use anything you want. Fixture boxes can be suspended by a bar that crosses the Tbar grid plus wires that transfer weight to the actual supporting ceiling above.

Thanks for the info, but what I'd like to know are some of the more pleasing options for lighting fixtures and their placement. The typical ceilings I've seen use fixtures that normally appear on a smooth surface. I think they look busy when used with a grid system. Has anyone used small, low wattage can lights along the perimter of a basement room?

You can also use track lighting. They make a piece that goes on the grid of the ceiling to hold the track. From their you can use small track heads. This is just another option.

We used flourescent cans, track lights and wall washer lights in our basement playroom.

You could go with a nicer version of what you have right now..... Most manufacturer's make a 'basket fixture' which is something of an indirect type of light....
http://www.daybrite.com/brochures/137.pdf

or better yet, try one of the latest generation of recessed lighting, which is much nicer aesthetically than the fixture you are using now, and very energy efficient. Check out the recessed option here.
http://www.ledalite.com/download/pdf/Voice.pdf

These are typically commercial products, but since you already have a t-bar ceiling, it would seem to make sense. One of these might run you more than a recessed can, but provide the light output of many cans, and without the glare....

We use track and the lights that are on the ceiling fan. Hate the ceiling fan lights and only use them when I need real bright light. Otherwise we use table lamp 99.5% of the time.

Bumping this.

I am looking for something like the Ledalights linked above. I can't find an on-line source for these or similar. I'd like to know what they cost.

I feel like my basement suspended ceiling is already low enough....I don't want to even add clouds with a 6" profile. Maybe I should just get over that?

Wall sconces with up light and out light can provide nice ambiant light. Then focus on task lighting where you need it such as pendants over a bar or table and accent lights like track for focal points on the wall. The rest of the room will take care of itself.