I switched this site to WordPress.com last weekend — it had been self-hosted since 2005, on Dreamhost.
Things went very smoothly — I followed instructions in the WordPress.com Support documentation and in various dashboard screens, and they were very helpful. I especially was impressed with the Google verification steps and how easy it was to add MX records for my Google Apps integration.
Probably the most annoying thing was waiting for propagation after updating nameservers, but there’s not a lot I could have done about that anyway.
A few hiccups:
- Old email subscribers: I had to email my old list to ask them to subscribe again on WordPress.com (I was using FeedBlitz before).
- Link importing: I had to split up the OPML file to import with categories, otherwise I’d have a flat import with no categories.
- I used Textile on my old blog, so I had to run a small PHP script to update the content in posts/pages to plain old HTML.
The plugins I’m going to miss the most are:
The Sensible Leader 