The changes made to iCal in OS X Lion have definitely been polarizing, and even some of the novice Mac users I know have found some of them questionable. The word "fugly" has come up more than once when discussing iCal's new faux-leather trim, an interface choice that makes a little more sense on the iPad than it does on the Mac. Macworld came up with a few tips to dispatch some of the annoyances introduced in OS X Lion's version of iCal, including the new UI elements.
Rather than copy all Macworld's tips here wholesale, I'll recommend you head there and check their advice for yourself. I will highlight one of their tips: getting rid of that execrable leather trim is not only possible, it's quite easy via a third-party program called Lion Tweaks, recommended by Macworld. The application bundles together several of the Lion-related tweaks covered here and elsewhere in an interface that's about as simple as it gets. Reverting iCal's skin to a nice, bland aluminum took less than a minute, and my eyes thank me for it. It's a modestly "hacky" solution to a purely aesthetic problem, but it's preferable to that oddball skeuomorphic design.
Even after implementing all the recommended tweaks, it's worth noting that the article writer himself says that ultimately, "Use a better calendar program" is his top recommendation. For my part, the only reason I stick with iCal on the Mac is its integration with the Calendar apps on the iPhone and iPad via MobileMe (and soon iCloud).
Apple OS X Yosemite