What version of DayPilot do you use? 6.2.2140 added some code to prevent memory leaks in IE and it's slowing it down quite a lot. It has been improved in 6.2.2154 (SP2). The speed should be comparable in all browsers now (IE was always the slowest one but it should be the same order of magnitude).
Yes, no problem. Please send it to support@daypilot.org.