i have google sync to iphone with multiple calendars. i've only had iphone a month or so i had google sync the entire time and for me its been flawless. no issues whatsoever. just works well.
I have found Google sync for calendars to be very reliable, in terms of reflecting identical data on the phone and on the Google Calendar site. However, being Exchange, there is no support for direct control of the colors of the calendars when using the native iOS calendar app, and there are various other small issues that make it less than ideal for syncing multiple calendars. However, I generally live with it, since I share calendars with others and they're all with Google.
I have been a MobileMe/.Mac/iTools user since 2000, and recently gave their updated calendar another try, and I find it dang near flawless. The colors sync on iCal on my Mac, iPhone, iPad, and on the .me website, and after a month I have yet to have anything missing or messed up. A big fan of it so far.
The answer to control of your colours on multiple calendars on the iPhone is to use a 3rd party calendaring app like CalenGoo. That way you get more Google and less iPhone.
I use Google Apps, and Calendar, Email, and Contacts work great. I also have Mobile ME. I just wished it was a more reliable service and cheaper, too...