My girlfriend and I also hated Sideways, unfortunately for us we bought it without watching it first (almost always recipe for disaster). This movie got such great reviews, but I was just sitting at the end thinking how pissed I was that I spent 15$ and wasted 2 hours of my life on this colostomy bag.
If cracking a half smile once or twice is worth 2 hours of your life then by all means give it a look, but I would rather listen to Maguire say "Let me tell you something" 400 times then watch this movie again.