I know that probably U9 is the weakest Ultima of the series, and I have this idea of playing it right away, before all the others (that I will play in chronological order).

Do you think spoilers could ruin story in the other games or U9 plot is somewhat disconnected from the others?

Actually, from what I understand, Ultima 9 contains "spoilers" that *contradict* the earlier games in the series.

My understanding is that the dislike for Ultima 8 and 9 is largely due to players expecting them to be like earlier games in the series, which the games are not. (Well, Ultima 8 *does* have bad controls, and Ultima 9's system requirements, to my understanding, were not reasonable on release, so the differences aren't the *only* issue, well that and the contradictions I mentioned.)

Also, I'm pretty sure that Ultima 9 isn't the worst Ultima game in existence, even with its issues; that would likely be the NES version of Ultima 5. (NES Ultima 3/4 and SNES Ultima 6 are all at least decent; NES Ultima 5 is not.)

Edit: Also, I haven't played Ultima 8 or 9, mainly because, unlike earlier games in the series, the main character is always male, and I strongly prefer to play with a female Avatar.

Yeah, the game takes a big dump on previously established lore, so you can just as well play it first.

I agree. U9 is not a bad game at all - actually it's quite good.... it's just a bad Ultima game and even a worse successor and final for the Ultima lore.

So play it not as an Ultima but as a regular RPG and be amazed when some of the names in Ultima 1-7 sound vaguely familiar afterwards ;-)

No, you can freely ignore the story of Ultima 9 because as dt says, it has a massive array of plotholes so large as to make Star Trek's Argus Array look small.