Ok, I've got 2 gigs of ram in my main system. I've got a 1gig dual channel kit from Geil (2X512) that are single bank, and a dual channel kit from Patriot (2X512) that is dual bank. Is there a difference in the bank styles (single vs. dual) and is there a difference in using two different brands? I'm just wondering. Both are coming up as dual channel, it's not an issue, just more or less curious on the differences.

It's only a question of density. ;)

The modules with 512 MB and single bank have a higher density per bank, the ones with 512 MB and dual bank a lower density.
Some older mainboards couldn't address the modules with one bank (thus higher density) or they couldn't address more than 6 banks (thus if you have 4 slots and 4 dual bank modules only 6 of the 8 banks are recognized).
Furthermore the older Athlon 64 weren't able to address the memory at 1T if there were more than 4 banks so if you had 4 dual bank modules you had to decrease the timings, thus you had less performance.

I think it's still impossible for any System (except Server Boards with Reg RAM or the new FB-DIMMs) to run at full speed with all RAM Banks occupied.

If it still works anyway @ max speed, it's out of pure luck.
4 Single Banks on Single-Sided Modules produce the least Noise on the Memory Bus though, therefor they have the best chances of reaching top speeds even at full RAM loadout on the Motherboard.