I bought one of the '07 Fisher Calibers about a month ago, and have been really, really pleased with it. I had a Specialized hardtail for around a year and a half, but never really got along with it. Either I was over the bars about half the time, or fixing flats on the back tire. The Fisher bike handles a lot better, and I'm finding I can get away with a lot more stuff than I could think about on the old hardtail. The "Genesis" geometry and its women-specific variant, "Genesister," is well worth trying out.
I looked at the HiFi, but they hadn't shipped the 29er version yet, and moving up to a 29er was the prime reason for shopping for a new MTB. The HiFi 29ers just hit the LBS last week, but I still think I got a better deal on the Caliber.
Whether you go for the HiFi or another Fisher variant, take some time to try out the 29er version...Those big wheels take just a little more motor to get rolling, but their momentum, speed, and the ride they give are derned hard to beat...
Here's my Caliber... They'll probably be a different color for '08, and the HiFi's I've seen have been mostly blue, but the sour-apple green color appealed to me just as much as those big ol' wheels...