In response to cost, I have many people looking for carpet tiles because they think they are cheap like cheap vinyl stick on tiles. But mainly what we have are high quality commercial carpet tiles, and I end up selling them broadloom for a lot less.
Beaulieu used to have residential carpet tiles. That was quite a while ago I saw that and I don't know if they still have them. If I recall, they looked like interlocking puzzle pieces.
Some parts of the country don't need to worry about this, but here in New England we need to worry about moisture. If the carpet tile is going down on concrete (most of the time for us), do a moisture test on the concrete. If you do a moisture test and inform the client of the issue, it is their problem. If you don't do a moisture test, it becomes your problem. Excessive moisture can destroy the pressure sensitive adhesive and turn it into mush. It can cause the tiles to shrink. It can cause the corners to curl.
No matter what the instructions say, let the tiles acclimate on site. They should be installed in a climate controlled building. We've had big issues with contractors that think they know flooring that wanted us to install in cold weather (sometimes freezing cold) in an unheated building. Other times, we've gone in a building that didn't have working A/C yet in the summer, and between the concrete, fresh wall board and spackle and everything else, the walls are moist to the touch. Ummm. No. That won't work either. Sometimes they put a couple torpedo heaters in a freezing cold building and turned them on when we arrived, despite assurances that the building would be "heated". They just don't get it.
The appeal of carpet tile is heavy traffic areas. It is relatively easy to replace carpet tiles in a heavy traffic area (or a stained tile). I'm not so sure this is a benefit in a residential setting. You should be sure the client gets extra carpet tiles when they order the original job, because they may not be available later.
One thing I will say about commercial carpet tiles: Most of them do stand up to a ton of traffic.
And another benefit: You know how you can make excellent seams in broadloom and the client complains about the seams. They point it out to you, and the seam is actually two feet away from the area they showed you. Well, despite carpet tile being nothing BUT seams, you won't get any seam complaints. I don't know why this is, but it's an interesting part of human psychology.