I have used several. Here are my thoughts, ranked by my choice from favorite to least favorite:
Ortleib bike-packer plus: These are my favorite. I put my clothes on one side, lunch bag in the other, along with my toolkit, spare tube & locks. These are large, and I wouldn't carry them if I didn't have secure bike parking. When I get to the office, I leave one bag on the bike (the one with lunch/locks etc.) and take the one with my clothes along with me. It fits my shirt/pants/towel/toiletries/shoes easily with room to spare.
Pros: Easy on/off even wearing thick gloves; easy to carry; fits all my stuff easily; waterproof.
Cons: I leave one on the bike during day/not viable in non-secure bike parking. The alternative: carry two very large bags, also not desired.
Topeak MTX Trunk Bag: My second favorite bag. The attachment is easy quick and secure, the trunk itself is good for leaving on the bike and carries toiletries, spare tube/tools and locks. The panniers zip out, and give good room for most of my stuff. I can't use my usual lunch cooler with these, and I need to leave my work shoes at work when using this bag. One side is taken up with my clothing, rolled. The other side carries my towel. When I need to carry my laptop, I can leave one side closed, and use my
Arkel briefcase on the other. I leave this bag on my surly troll most of the summer for when riding around with the kids. I can put all their stuff in it easily or leave it closed. It does require a topeak specific rack.
Pros: Easy on/off even with thick gloves; can be paired with laptop specific bag when needed, nothing left on the bike during the day
Cons: Requires proprietary rack, not quite large enough to carry all my junk for the day. Not waterproof without separate cover
Arkel briefcase: I only carry my laptop in this bag. It has a lot of room but is VERY large and is prone to heel-strike unless you have a long chainstay (I do). I wouldn't consider this viable as an all-purpose bag, only as a specialty bag, so this is the extent of my review.
Arkel Bug: My bug is several years old and has the old attachment system. Still, I needed something that would hold up in sub-zero temps that I could put on and off the bike easily and this did the trick. No room for lunch or shoes, and I had difficulty keeping the lock in it easily. Use as a backpack is nice, but I found I didn't use it that way much. Not waterproof, but I purchased the cover and never had trouble with water even in heavy rain or when slush was shot all over it with the cover on. I stopped using it when I got the MTX bag since it is not as convenient and I couldn't carry as much.
Pros: Solid quality in all weather
Cons: Backpack usage not that comfortable, not waterproof without cover
Nashbar Garment Bag Pannier: I hate this bag for everyday use, but when I need the jacket or must be sure there are no wrinkles in my clothes, this is the bag I use. I've never used it in rain, and while it looks to be decent enough quality, I'm not sure it would survive daily winter use. It is also huge on the bike, sticking way out the back. The mounting is confusing until you get used to it also. The biggest pro for this bag is price. If you must wear professional attire daily, this is a good bag. Beware that you need to use wire hangers, it's not big enough to handle full sized jacket hangers.
I have tried a few other bags here and there, but these are what I have used regularly for a long time now. Good luck with the search.