I'm a newbie to go. And I spent a lot of time to promote to IGS 9k... I would like to know how strong is compared to KGS and tygem.

I used to play on tygem, but there are too many (at least I feel) sandbaggers in DDK or even SDK. I was 7kyu, but feel really bad with sandbaggers so I gave up.

I also played some games on KGS. But the system there for me is a little strange. Besides, I don't play frequently, as a consequence, my rank just keep going up since my opponents got stronger later so I also level up...

That's why I focus IGS now. OMG, all my opponents played several thousand games... And they still 10kyu or 9kyu... Is that possible... Now I promoted to 9kyu, and I feel I'm much stronger than when I played in tygem or KGS. Is that true that IGS rank is more solid?

Have a look at http://senseis.xmp.net/?RankWorldwideComparison

It's a comparison of ranks across different servers.

Thanks!! How accurate is that?

It's decent, though some of the data might be a bit dated. Online-go just did a big survey comparing ranks (results are linked from that page); last time I looked at it the data was still pretty raw but it is recent.

For one data point to confirm the chart, I'm about 6K on KGS and 8K on IGS. My IGS rank might be lagging a bit behind my true strength, though. I just got promoted and was regularly beating my opponents b a large margin.

Of course, the chart is just generalizations. Different play styles or playing circumstance (I always play on IGS with my iPad while I sit at thr computer for KGS. Does that affect my play?) could mean any individual has greater or lesser variance than average.