I LOVE my Arkel trunk bag, but not so much as it pertains to the Randonneur rack. I have one, and even with a light load in the trunk, it makes the rear of the bike "whippy" when you're climbing or out of the saddle. I tried it with both extension arms, hoping that by using the longer brackets, it would lower the load enough to get rid of that whippy feeling. It didnt work. They rate the rack to be sutible for around 13 lbs; I came nowhere near that and had issues. Here's a pic for reference for those who haven't seen a Randonneur rack

The pic shows the rack installed with the standard brackets, and you can see how high the load sits. I installed the longer brackets after this pic was taken, which were four inches longer, but not nearly long enough to prevent the whippy feeling. And before anyone chimes in to say Ti is whippy- you haven't seen the pipes on my bike. It's built like a brick Sh$T house.
Standard racks? Heck yes- they make your bike truly useful, and like others have mentioned, you wont know it's there until either you need it, or it's loaded.