The J/27 is marketed as a weekender and sometimes called a Racer/Cruiser. While you can technically sleep 5 aboard this is not likely to ever happen or be desireable. The boat can sleep 4 if necessary and the the bunks are long and with good cushions quite comfortable.
There are some serious drawbacks with the boat which I will list first. If you plan to read these then I ask that you read further to hear what is great about the design.
Headroom? How can you even call it Headroom when it is 4' 5" ?
Head: Most have a portapotti and some a marine head forward of main bulkhead. It is serviceable but you need to be a contortionist to use it.
Galley: most come with a sink, stove and icebox. The icebox is good but the sink drains into the bilge and although there is a faucet there is no tankage. The stove is very good quality but I doubt that many have ever been lit given where they are located.
Storage: Some under vee berth and settees but little anywhere else
Cored Hull & Deck: Many have wet decks which are easily fixed but some may have wet hulls which are not.
The cockpit is enormous. The decks are very open and easy to move around.
The boat sails incredibly well. It has a PHRF rating faster than many 35 footers of 1980s vintage.
This boat can plane. It is light and some have achieved speeds in excess of 17 knots!
Deck is well laid out with all sail adjument gear.
Initially boat feels tender but is very stiff once it heels.
Very easy to work on this boat as there is no headliner and the underside of deck is accessible - everywhere!
Sail costs are kept down by a fractional rig.