One reason to use IE8 is if you want more battery life. They ran a test not too long ago.
Other than that, the only reason I use IE8 is for the 64bit version when I don't want flash or java loaded. So when I visit sites I'm not sure about their security, I feel more trust with IE8-64 since I don't have either extensions installed for it, so I know I can't get attacked by malicious flash etc.
Chrome is nice and fast, especially on older PC's. But speed is not the concern for my personal computers because they all have 4gb memory or over, so I can withstand the ~900mb-1gb large firefox process without issues.
One reason I don't like chrome is due to the adblock sucks ass on it, second is I'm not wholly trusting of the security in Chrome. But I'll trust Chromium over Chrome.
That being said, the best personal browser I use is still firefox loaded with all the things I need. Adblock, BetterPrivacy, Noscript, gmail extension, just these basics and I know I can be very secure about browsing habits.
Startup loading speed is not my concerns.. The rest while in the browser loading, feels the same between all of them or I can't tell a difference.
