You've seen the results, so you might not even need my advice anymore. For anyone sensible looking for a new platform i820 should be pretty much out of the question.
This half-baked Intel-chipset doesn't perform well enough and requires very expensive memory too. If you are on a budget go for BX, consider VIA's PC133 SDRAM chipset or wait until the DDR-platforms become available.
Brent will post a first review of a DDR-platform soon. For the performance-hungry Coppermine-freaks there's only one chipset, i840! Motherboards with this workstation chipset may be a bit more expensive than i820-platforms, but you get top performance and some other nice features as e.g. a dual-board for it.
Considering the high costs for RDRAM, the 100 bucks more for i840 over i820 are certainly well spent and this expensive memory is completely wasted should you plug it into an i820-motherboard. Besides, Coppermine on i840 is making Athlon's life a whole lot harder ...