My husband and I each used a copy of Thunderbird on each of our (separate) computers. We used it for a year or more and were very happy - worked a lot like Outlook Express, and took care of spam quite well. But then Bill's copy started having a lot of "glitches" and eventually stopped working, so he switched back to Outlook Express. Soon after, my copy started acting "weird" and some folders became corrupted for no apparent reason. So I also switched back to OE.
But I still use the Mozzilla Firefox browser, and have a lot less pop ups than with IE. But there are occasionally times when it can't run a particular website, I think because I need a copy of something extra. Since I am not a computer person, it is easier to switch to IE for a moment now and then, rather than try to figure out why it doesn't work 100% of the time.