The final loan bid I had outstanding, for $200 @ 20.75%, was accepted today. This means I now have all of my $500 loan amount invested across four loans. My average interest rate is 17.82%, or 17.32% after Prosper's fees.
There must be some sort of strange rounding errors going on because my account shows Principal Loaned = $500, Principal Repaid, Interest & Fees Paid, and Service Fees all equal to $0.00, yet my total Loan Value is shown as $500.04.
Anyway, I'm glad all my funds are now loaned out. The final loan actually was scheduled to end in over a week, but it looks like the borrower closed it once she had enough bids to fund the loan. She could have left the bidding open to see if she could get a lower rate.
All in all, it's been a fairly good experience so far. If you are considering lending through Prosper, I suggest reading through the Borrowing help screens first, so you understand the process from the borrower's point of view. I didn't do this until later and many of my questions would have been answered had I read it sooner.