I have no first hand knowledge of HitchHiker seal issues but that doesn't mean they are not out there. It would be on a case by case basis because a seal issue(s) can also boil down to a maintenance issue rather than manufacturer defect.
If a manufacturer has a good reputation, it still means there could be one or more units out there with problems.
When buying something like an RV, please take the time and effort to look along all the roof, wall and floor seams. Any stains on ceiling, wall or floor panels could indicate leaks or mean other problems. If everything goes well and passes your inspection with no soft spots on the floor, the next step is to have it inspected buy a good rv technician.
The money you spend on that inspection could save you thousands on something you and the previous owner missed or tried to hide.
Each spring and fall, I use chemicals on the slide seals of our TT to keep them in good shape and inspect them. On our 04 Prowler bought in 03, I have only found two broken screws in the bottom panel that holds the bottom slide out seal in place but still zero leaks.
Cost there was a packet of a few stainless steel screws.
Goodluck with your shopping!