It's been out for a couple of weeks, and only two or three issues have turned up so far:

1) '-' DS names for RRD don't work right. There is a simple code change that should have been added between 0.9pre3 and 0.9, but somehow didn't get into the final zip.

2) I want to add some more checking and explanation for the GD alphablending issue. It's mentioned in the FAQ, but it seems that it maybe affects more people than I expected.

3) KILO handling is wrong again. Again, it's a fix that got lost somewhere.

4) Using the MRTG-HTML data source with remote files is broken in 0.9 -it's a simple fix, but actually I'd forgetten all about this feature.

So there will be a 0.91 to fix up these things, and maybe add a few tweaks. I'll wait a week or so more to see if anything else turns up before putting it out though.

If you are being bitten by #1 here, the fix is one line:
in lib/datasources/WeatherMapDataSource_rrd.php add a new line above line 196:
$inbw = 0; $outbw = 0; // ADD THIS LINE
if(isset($values[$in_ds]) ) $inbw=$values[$in_ds] * $multiplier;
if(isset($values[$out_ds]) ) $outbw=$values[$out_ds] * $multiplier;