I’m a heavy user of Google mail/calendar/notebook etc. This is a part 1 on some of these Google products, and how I think they can offer a better user experience, with what I think are potentially low hanging fruit.
I have a bit more calendar feedback than others, hence devoting an entire post on it. So here goes:
Multiple reminders: be abled to have multiple reminders for each of my calendar events (eg. 1 week, 2 hours). NOTE: Seems this feature got implemented sometime in the last 2 weeks or so… Google can read my mind! 
Repeat Whenever: Be able to repeat a event at $n$ future dates. For example festivals happen on different days (Chinese new year etc.) Not all events happen at regular intervals.
Reminders for non-default calendars: Be able to set reminders for events not on default calendar? NOTE: Even this got implemented as of May 3, 2007. Read here.
Events at non-day/time resolution: Putting events at the month/year/week resolution? For example year of the pig, month of excitement, week of joy? I can’t describe these events without making an event that has start and end dates of appropriate length. You can imagine the messy look on my calendar if I describe the year of the pig as a year long event!! This feature would be on the lines of an “All day” event.
Better repeats: I’d like the capability to be able to put events at the level of “last day of month / middle of the month” etc. I know last friday or the month is possible, but I don’t happen to be able to use it (yet). The repeat whenever feature I mention above is slightly different than this one.
Better reminders: Reminders at $n$ days before an event? Currently its maxed out at 1 week?
GTalk integration: How about showing me as busy on GTalk based on my calendar events, if I’ve marked myself as busy on my calendar? Not sure if everyone would want this, hence this could be an optional setting.
Hopefully someone on the Google Calendar is reading this (and my mind!)
UPDATE: How could I forget to request a J2ME app for Google Calendar, similar to Gmail Mobile. Am sure Google is working on this, given the popularity of their current mobile offerings!