I jumped on the Firefox bandwagon a few months ago. I’ve been very happy with it. It’s extension mechanism is fantastic, and couldn’t be easier to use. One slightly annoying thing is that search engine plugins can only be installed system-wide, which seems a bit silly. But this has already been listed as a bug by others and is currently being fixed. If you want to make the switch from another browser, especially the evil one, please click the Firefox image in the left margin.
I’ve also switched to Thunderbird from Evolution at home and at work. I found Evolution to be exceedingly slow when my Inbox got large. Thunderbird has not displayed the same problem so far, dealing with exactly the same number of messages. Unfortunately, Thunderbird will not import mail from Evolution, so it has to be done manually. Since Evolution and Thunderbird use the standard mbox format, it’s just a question of copying your inbox and subdirectories to the relevant place in your Thunderbird profile folder. That part takes all of ten seconds. The tedious part is having to set up all your mail filters again. Thunderbird has a great spam detection feature which has been working really well for me so far. Another problem is importing your address book. Thunderbird will only import LDIF, CSV and a few others. Evolution will only export vCard. Therefore, you have to find a way to convert from vCard to LDIF or one of the other text formats. Since my address book wasn’t too large, I found it easy just to recreate my address book by hand. The "Add to Address Book…" item in the context menu that pops up whenever you right-click an e-mail address in Thunderbird expedited this process somewhat.
