Hi there, yes I'd say it is if it is near perfect with only 100 hours on it.
I had a 535 10 years ago, sold it for a brand new Solent 540 (same hull) and are now back to another Ribtec 535.
In my view they are quality well built good sea going boats that if looked after should last for years and years
Yamaha are the best engines and the two strokes are the best Yamaha's, some may challenge that.
100 hours is fantastic, you could pay less for a boat and then end up spending loads to sort it out. If it's what you want and it fits in terms of colour and spec etc., I'd buy it quick before someone else does.
Only my view, it's your call. Keep us posted.