I got the 18ah for my 1150. It sat on the shelf for 6 months and then I was going on a 10 day trip and since the original (yes, 7 years) BMW (Exide) battery was getting a bit tired, I swapped it out for the Shorai. Big mistake! Every time the temp dropped below about 50F overnight the bike was very hard to start. I did the lights on thing to warm the battery but it was hit and miss and it caused me stress every morning. After the first start, no problems for the rest of the day.
The slow cranking and low voltage is very hard on the starter and the servo brakes. The Shorai would drop immediately to around 9.5v on attempted start and spring right back to 13v when the starter was released. The 18ah Shorai has a much higher CCA rating than the BMW or Odyssey batteries; I have to say that the CCA ratings are crap. CCA is supposed to be at 0F and I can't see a LiPO cranking anything at that temp. In Canada, we plug our cars in at night (in the winter) and battery blankets are readily available but I don't really want one on my motorcycle!
I ordered a new Odyssey and it has been flawless. I did call Shorai (great customer service) and they sent me a 21ah replacement but now that the cold weather is here, I'm not putting it in the bike. Maybe I'll try it next summer.
There is a great thread in Parallel Universe on LiPO's http://advrider.com/forums/showthread.php?t=770364