Opera probably hasn't been optimized for 10.2, even though their site states that it works with 10.2.
If you use if for previewing your sites how they look in Opera with OS X 10.2, it has probably really really small marginal ... 5 % of all users in Mac, of which max 10-20 % stil in 10.2, and of those maybe max 10 % in Opera, with a very optimistic guess.