I use an Arkel Bug in Wisconsin. I've used it for 2.5 years and thousands of miles, hundreds of on/off the bike in all kind of weather. I can't find anything I don't like about it other than that I'd like it to be a tad bigger. Something tells me this would be the case for any bag, so I don't count it as bad. Here's the review:

The good:
After this much use, it still looks new. The fabric is great, and even without the rain jacket it's mostly water-proof. The attachment mechanism is great. I rarely "lock" it into place though, and on/off is simple to do, even in the coldest/wettest envionrment. I can easily fit a day's clothing, toiletries and shoes into the thing, and when I get to work, I simply pull out one of the straps and fling it over my shoulder for the 600 yard walk to the locker room.

The okay:
Without the rain jacket, your stuff will get a bit wet in a downpour, but those happen so rarely here, that I routinely forget it unless its needed in the morning. If you live in a rain enriched environment, I'd say it would be needed. I also always want just a hair more room. After the clothes/shoes/wallet/id-badge etc., there's no room for anything else. This isn't a problem for commuting, but when I go on day-trips, I find it is a little short on room. Then again, that's not what it was designed to do.

The bad:
Initial price is a bit high, but I think it was well worth the price now that I'm 3 years into it and don't see any evidence that its been used.

My suggestion: Figure out what you want your bag to do. If the bug's dimension & use matches with that, pay for it up-front, and know it will last a very long time.

BTW, I also have an arkel handlebar bag, and I'm less fond of it...lest you think I'm a shill for the company.