It's quite expensive, but the BPS 100MPH is tough to beat. I have had one for 4 years and every time it rains, I'm reminded that (for me) it was money well spent. Dry as a bone no matter how intense the downpour, even ripping at 50-60mph.
Like anything, it's all about being able to justify the expense to yourself so cheaper options are out there, but something with a Goretex (or similar breathable membrane) is really where it's at for keeping the rain out while still allowing any moisture from your body to escape. For what it's worth, I also love wearing the bibs on cooler summer or fall mornings: they're 100% windproof as well?