I have use CCS and HTPIC C and I recommand you CCS is very complete. It's come with all library rs232, i2c, timer etc... and some driver lcd, real time clock etc...
CCS is not an ANSI compliant compiler, it is more like K&R C. There is really only one danger with CCS and it has to do with the 30-days of free downloads option. Typically whenever you see that new chips have been added that means new bugs are present too. Lately the updates to CCS have been about one per month, but it is not unusual to have three updates in one week.
The best thing to do with CCS is buy the full year package, which allows you to download the updates throughout the year. Keep all the ones you download since sometimes you might have to back-track if a newly introduced bug stops you from development.
I use CCS here and I'm very happy with it. It's not ansi, but once you figure out its quirks its as good as anything else. The built in functions are ok. You usually end up doctoring them up a bit. Some register manipulations can only be done under asm. They also have a good active user forum. Good Luck.
CCS is very used in Brazil, some developers like this C compiler because are easy utilization and have many libraries.
I use CCS at any years and look many advantages...check the compiler page and realize your comparation...
I use CCS and I highly recommend it. Easy to use and build in fuctions, atleast you can save your time in writing the functions yourself. Use CCS if you have only a few projects or otherwise go for ANSI C compiler which is definetly HTPIC.