At one point, I was looking at the Oly myself and rejected it based on what people here have already said. There are some in the photography world that complain that Pentax doesn't have a large enough lineup of lenses and they simply don't know what they're talking about--how about 40+ years worth of lenses? Sure, you can use the old OM lenses on the Oly DSLRs with an adapter, but from what I understand, they don't work very well, though. I've seen some excellent shots produced with Pentax lenses that in some cases are older than me.
If you want to save some money, you might consider getting a gently used K10D, which are running in the neighborhood of $500-550 or so--that's how I got mine. The Marketplace is good place to pick up one, as there have been a lot of people that are upgrading to the K20D and need to sell their K10D to finance part of the K20D purchase.
Put your money into good glass. Bodies will come and go, but if you get the good glass and take good care of it, it'll last and last.
Heather