My old roommate still works at Charter in the corporate office and I worked there for 3 years doing internet/phone tech support at Charter Commons in Town and Country, MO (the 7th layer of hell) from May 03-Sept. 06 so I will try to defend here.
I am in a ATT exclusive apartment complex in South County that has wiring so old, the 1.5 Meg down speed is the max I can get. I would kill to get Charter's 15 Meg connection, even with this cap.
Charter has worked very hard over the last year to get their HD, data, and phone technology to the level it should be at. Charter is the first cable carrier to get the DOCSIS 3.0 service (FIOS speed) out to the public for sale. Independent reports show Charter's tech infrastructure to be the best of any of the cable companies. They also have an HDTV lineup that rivals DirecTV/Dish and has less compression/better quality than Comcast's. Their new Moxi DVR's are very good, but are REALLY hard to get. My former roommate had to use his connections to get one. Problem is they have so much debt from their lowsy executives from 00-06 that the hole may be too big to dig out of.
Also if Charter's service is intermittent or not working even after multiple tech visits/mainline calls, then by all means switch. I had to deal with those issues hundreds of times and don't blame anybody for switching.
My feeling is Charter's cap is not too bad, at least for the 15 meg level. It's the same size as Comcast's, and as long as you're not doing bit torrent stuff, you should be fine. Now ATT will have a cap, it's just a matter of when and what size. From the rumbling's I heard a few months ago on DSL Reports, it's probably going to be much smaller than the Charter/Comcast ones.