never encountered all the thing you mentioned. Unless you're a very birdy person, ebayers dun anyhow cancel people's bid. shipping is from 3 days to 1 week to your US address, never heard got people waited until 2 weeks then receive the stuff @ US office. Just curious, how many times have you used ebay? I have been buying close to 10 items from ebay for the past 3 months.
As long as you're not getting 2nd hand stuff, there is no argument involved. You deal direct with iRobot for any dispute, not the reseller. So, does it make any difference?

unless iRobot is paying 100% to take back ur stuff if you buy direct from them. But if you use your calculator, dun need brain, to calculate, it's much more costly to deal direct even if there is RMA involved.