Aerostich gear is great. I recently bought the Darien for my commute. I love 'em. I wear work slacks underneath and they come out fine. I haven't had the opportunity to test 'em in a downpour yet, but I've been in normal rain for 20 minutes a couple of times and the pants were perfect. They fit me well and you can get 'em altered if you like (which is an extra $50).
The downsides -- as I'm sure you know, they are expensive. Also, the knee armor is a little wide, which is great for protection but more awkward for walking around. And hip protection is sold separately which adds to the cost.
If you are willing to part with the cash, they are a great choice.
I have the Darien Light jacket and pants. They are great. They take a while to break in, and I'd agree with the comment on the width of the knee armor. And unless you get the hi-viz yellow you won't look like a space alien when you walk in the office.