First, I've only just started using myibay, but so far it seems to work well. Nice work so far.

I'd like to propose a new feature. Often, I'll want to bid on multiple items from the same seller and take advantage of his combined shipping discount. I also take shipping costs into account when I calculate my max bid, so if I'm willing to pay $20 (total out-of-pocket cost) and shipping/handling charge is $5, the my max bid will be $15.

Now, if I win that item and the seller has a 2nd item I'd like to buy (also for $20 total out-of-pocket cost), but his combined shipping policy means that he'd only charge an extra $1 for an additional item, then I'd be willing to bid up to $19 for the 2nd item.

I'd love to be able to tell myibay something to the effect of: "If I win Item A, bump up my max bid for Item B by $X."

A similar feature was requested and it's currently in ToDo list right now.
It's not under a higher priority, but should be implemented some time soon.
Thanks for your suggestion anyway, I'll pass it to the development.