I do understand the convenience of having it, and maybe I'm so against it because currently it is only my wife and I that travel, so 2 suitcases pretty much cover us each trip. Maybe I'd be more open to it if we had to pack 4+ bags.
For us, taking less stuff is a big deal. There are 3 of us - DH, DS8 and me - and just taking things I feel are necessary for a Disney trip, like an extra pair of shoes so we can switch out takes up a lot of space. (And usually we're packing 2 pair of shoes each because we're traveling from cold NY to warm FL, so the shoes we wear when we leave home are not appropriate for park touring.) Then if I want to keep up my running, I have to pack running shoes, which I absolutely cannot wear in the parks. Then there's the stuff that we ONLY use at Disney, like lanyards and pins (which take up little space but man, they're heavy), mist fans (who wants to keep repurchasing those at $15-$20 a pop in the parks?), ponchos. Never mind all the toiletries that, if packed, would force us into checking luggage.
Then there are things we absolutely would otherwise buy because we're in a villa - like laundry detergent. It gets frustrating when you always have to throw out half of the smallest bottle you could find at Publix. The same with bleach that I use to clean out the jacuzzi. (I'm sensitive to the bubbles and stuff people sometimes use in those tubs.)
So Owner's Locker lets us keep some of that stuff down there, including extra clothes AND stuff we'd never otherwise pack, like a coffee grinder, a Brita pitcher and filter (I hate, loathe and despise being dependent on bottled water, which is my environmental pet peeve), etc.
But the stuff is only part of the reason it's worth it. In our family, I am the packer. I'm the one who would put all the Disney stuff (ponchos, Pal Mickey, pins, Hidden Mickey book, mist fans, etc) in one spot and then drag it out for each trip. I'm the one who would have to put together all the toiletries, clothes, shoes. Multiply that x2 for our average 2 trips per year, then factor in that all that stuff has to be unpacked and all the Disney-specific gear stowed in its "home." I work outside the home at a very demanding job that already has me traveling around the world and packing and unpacking a suitcase all the time. Frankly, my time is WAY more valuable to me than what we pay for our Lockers every year. Yes, multiple, as in we have 2 very full ones now and a third Locker being delivered on my next vacation. I spend so much less time packing because of our Lockers AND we can travel carry-on when we want to. (My son still uses a booster seat, so we often check that anyway.) We usually fly Southwest, so checking bags is not an issue, but not having to wait at baggage claim or not having to spend time in line at the airport ticket counter is a great thing.
Owner's Locker is certainly not a necessity like food and water. And it's probably not for every person. At first I didn't even think it was for me, and my husband certainly thought I was crazy. But if I had a nickel for every time he said "Hey, do we have ____ in our Lockers? We should add it if we don't." The other day in Target, my son and I were walking down an aisle when he stopped, said "wait a second" and turned around to go get something we'd already passed. It was a water bottle with a neat flip up lid. He said, "Can we take this to Florida and put it in our Owner's Locker?" They're as crazy about them as I am! And as DVC owners, as our trips become more relaxed and less park-centric or less about commando-style touring, we're spending more time in our room. Being comfortable there is more important than ever before. I
LOVE
that I can keep a lightweight fleece throw (purchased in MK as one of those "purchase with a purchase" deals in 2008) so the air conditioning the rest of my family loves doesn't chill me to the bone. I LOVE that we can keep a scrapbook where we record each of our trips - what a wonderful keepsake that will always be! I LOVE that I never again have to remember to pack phone chargers or rechargeable batteries.
And I haven't even talked about the wonderful customer service! It really can't be beat. Brian and John have built this amazing little company that is truly customer focused and they are really good people. The reason I know this is true beyond my own interactions with them is that I actually talk to bell services people - they have nothing but glowing things to say about Owner's Locker. And it could be VERY different because adding those Lockers to their work every day could have had elicited a very different response and attitude. But John and Brian have worked hard to include bell services in their work - taking their suggestions about drop off and pick up processes, labeling tips, etc. And they treat bell services staff like partners - they could do all the great work in the world, but if bell services didn't care for people's lockers, the result would be a lot of unhappy customers. All this adds up to me having a TON of respect for them as a company aside from all the personal value I gain from using their service.
Had it for the first time last trip and for the first time ever we didn't go home with an extra case and all our bags were lighter! 
The CM at the desk when we checked in was like "where's your luggage?" 
I said this is it!! He said he RARELY sees that for a trip longer than just a weekend... I just beamed over our Owners Locker!! But we also don't currently have any more trips planned to FL but I am still glad we have our locker. We're going to HHI in August and going on a Europe / MED cruise vacation in 2011. I would LOVE to be able to slip in a trip in though. We'll see. Not sure if I can hold out or not...the plan was to save money for Europe by not buying new AP's again.
ANYWAY...LOVE our locker!! I will miss it this summer for HHI and for our MED trip next year!! It WOULD be nice to be able to rollover unused visits into the next year though. Oh well... I like knowing our stuff is waiting on us when we arrive!!
