I asked last month: how popular are Google gadgets? Niall Kennedy compiled some stats that could answer this question much better than my analysis.
Google has 3 times the number of gadgets from Netvibes, Windows Live and Pageflakes (Google has more than 4,200 gadgets). According to Niall's investigation, Google "served up over 700 million gadget views last week, including over 400 million gadget views (57%) from its top 10 gadgets". The most popular gadgets by far are Date & Time and Google Calendar, which are included by default in any personalized homepage. The most popular categories are: tools (includes Google Calendar), fun & games and lifestyle (includes videos, horoscopes). It's very interesting to note that 44% of the total number of page views were for the 28 gadgets created by Google.
Google Personalized Homepage grows much faster than the competition mostly because there's a link on Google's homepage that sends you there, but also because people found out that it's a good way to view information for different Google services in one place. The project was initially called "Google Fusion" and had the mission to become a glue for the growing number of Google products. Google should now focus on promoting third-party gadgets and the features introduced last week are in that direction.