I use an Aussie D30 in the front (not currently locked in the rear). The alloy and design of the Aussie may be slightly different than the LockRite, but the Aussie basically functions the same.
The front Aussie is invisible on the highway, so I'd guess that the Lockrite would be the same, give the design similarity. The Aussie, however comes with a replacement warranty regardless of what tire size you are running. I don't think the Lock-Rite does and I've read that people have had gripes with breaking the Lockrites and a couple of gripes with noise (at least when running one in the rear).
D30 Aussie runs $230 at Northridge4x4.com. If you really want a Powertrax lunchbox-type locker, maybe you should try the higher-end Powertrax No-Slip. It tends to run $400, but is made of a tougher alloy and is supposedly quiet versus the standard Lockrite. I was considering one of the No-Slips for the rear end on mine, but may do another Aussie there, too.
So, buy your friend's $100 LockRite? Well, sure, $100 is better than the usual $250 sticker price. But, you've got a lot more non-carrier replacement locker choices on the market these days -Aussie, No-Slip, Detroit EZ - versus 5 or 10 years ago, when LockRite was the only game in town. And, you don't really need a selectable because you are in consistently warm country. I'd personally spend another $150 and get the Aussie in the front - I don't think I've heard of one person having a beef with it and the warranty may come in handy sometime