I set everything up to bid on eBay item 190888485872 and my bid(s) were never placed. I'm running the 30-day trial version. Does myibay actually bid during the trial period?

Yes, it works during 30 day trial period.

If you check the status of your snipe (sent to your email if you specified it, or available in the Snipe window where you set your snipe amount, time, etc), you will see the following reason:
"Your PayPal account is not linked to your eBay account".

Please check the following FAQ section for more information:
http://www.myibidder.com/forums/viewtopic/647/your-paypal-account-is-not-linked-to-your-ebay-account/