I think for me, it's important to have both raid/w/g/private chans/bgs/p all at the forefront. I once had tabbed windows, but I found that often I'd completely forget about one ie. the whisper tab. Then I'd go back and find a long list of whispers or just one important one.
In terms of a combat log, I found it completely useless (only until recently) unless I noticed I got dropped fast and hard, and wanted to take a cap of some uber pyro crit or something, which I have many of :p (I play a warrior). So now, I just keep it tabbed.
Currently, since I am not in a guild currently and don't play on joining one anytime soon, I have one window visible. Long as I don't join trade or lfg, I can handle the /ra /w /p /1 and private chans. I think I like having less clutter on the screen, but if I were to join a guild, or especially a raiding guild, I's most certainly create another standalone window for guild chat and such.