Well, I know a year hasn't gone by, but it's been over 2 months now and, I have to say, I love this thing. I haven't used my hose vacuum once.

To answer the waterproofing question: it seems to be waterproofed very well. It's a pretty clever design, although I have to say the first time I used it I was a little apprehensive about plunging a piece of electrical equipment into a pool of water!!

As I say, I love it, but here are a few tips that I've discovered:
1) The filter bag is small. VERY small (which makes sense, bearing in mind the size of the device). It takes about a minute to empty the bag and re-fit it, and I recommend that you do so before (or after) every vacuuming session. Starting with a clean bag can help performance (especially if you've vacuumed up a decent amount of fine particulate matter) and it also allows you to unclog anything inside.
2) The manual says to recharge the vacuum after every single use for 8 hours. I've found you don't need to do it this often, but it IS important to maintain a decent charge on the vacuum or you'll find yourself just pushing dirt around the pool (I discovered this by experience!!). I've found that you can use the device for about 30 mins on a full charge (not necessarily in one go - perhaps 3 ten-minute sessions), and then it really benefits from a charge of at least 4-5 hours.
3) Leaves - forget it. Any leaf larger than, say, a quarter (or 10 pence piece to you fellow Brits), the hole in the bottom of the vacuum just isn't large enough to suck the leaf through. It's probably a good thing, too, as it wouldn't take many leaves to fill up the bag. I simply skim them off the bottom with the net once I've finished vacuuming.
4) The first few times I used it, when I lifted it out of the water at the end of my session, and held it over the pool to allow the water to fall back from the vacuum while I turned it off. DON'T DO THIS! I wasn't paying attention the first few times, but I eventually noticed that you get some previously-vacuumed matter fall back into the pool. It seems that the vacuum only operates under water - once it is in air, there's no suction so all of your dirt falls back into the pool!! I now move the whole thing away from the water, put up with the fact that I lose a few litres of water, and turn it off.

I'm very happy with this purchase. Even if the thing breaks every 6 months (and I'm not saying it will), it's worth the $150 to buy a new one each time, in my opinion.

On a similar topic - I have just returned from Home Depot, and noticed that in their pool section they now have a vacuum system that you plug your garden hose into. It has its own bag and, apparently the water pressure from the hose creates a vacuum, and it sucks up the dirt into its own filter bag. It doesn't use the pool filter. I've never used it, I have no idea how much water it gets through, or how effective it is, but it's only $25 in case anybody wants to try a cheaper non-pool-filter vacuum.

Cheers,
Matt.