I would say, with waterballast in - yes, very much so.
As above, depends what you mean by "stable". What do you mean?
Sailing manners are good, safe and steady. Self righting etc.
I've dipped the gunnells a couple of times when sailing alone (trying too hard in a blow?) and the boat has looked after me.
We've been out in some v strong winds, with a young, fit experienced crew.
See also some of the recent posts by user "anyone can uk" wrt disabled/restricted abilities usage.
As a picnic/beach boat - again yes, stable. You can get up and walk around in the cockpit as you like, with no fear of stability issues. The boat feels solid. Not dinghy-like at all.
I'm about 90kg dressed, and can safely climb all over the boat, including side, fore deck, and aft decks without any concerns about "tippiness".
We take a lot of non-boating friends for trips out, generally motoring (as sailing would probably freak them out on grounds of "string everywhere"?) No complaints of tippiness.
The Tideway we had years ago was quite the opposite. Wayfarer, Gull etc are similarly tippy.