I give a try to dynamic vardiff and I guess it is to aggressive for my setup ...
Here is one example with only one BFL single after I start the miner ...
It start with diff 1 (as expected) but in less than 2 minutes it switch from diff 1 to diff 15 .... and nothing found at this difficulty for about 8 minutes when it solve a new lower diff 10 share.
I think diff 15 or even diff 10 is to much for a miner using ~800 MHs.
I'll no give up on dynamic vardiff but for now I'll switch back to manual difficulty.
I guess I'll test it again from time to time to see if it is less aggressive
For reference here is my log:
[2013-03-30 16:51:42] Probing for an alive pool
[2013-03-30 16:51:43] Stratum from pool 0 detected new block
[2013-03-30 16:51:53] Accepted 876faaff BFL 0 pool 0 Diff 1/1
[2013-03-30 16:51:54] Accepted b29fb61c BFL 0 pool 0 Diff 1/1
[2013-03-30 16:51:58] Accepted 3e1ae57a BFL 0 pool 0 Diff 4/1
[2013-03-30 16:52:01] Accepted 94f8b8a1 BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:02] Accepted 35a99522 BFL 0 pool 0 Diff 4/1
[2013-03-30 16:52:03] Accepted 8ade807b BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:05] Stratum from pool 0 requested work update
[2013-03-30 16:52:05] Pool 0 is hiding block contents from us
[2013-03-30 16:52:11] Accepted f7a27f86 BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:11] Accepted 85480cb4 BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:12] Accepted 691be388 BFL 0 pool 0 Diff 2/1
[2013-03-30 16:52:14] Accepted 2b568e86 BFL 0 pool 0 Diff 5/1
[2013-03-30 16:52:15] Accepted a1459f41 BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:16] Accepted c78c95fc BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:22] Accepted 7944bf34 BFL 0 pool 0 Diff 2/1
[2013-03-30 16:52:22] Accepted 9ee17460 BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:22] Accepted b95bb77b BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:24] Accepted 3f2041dd BFL 0 pool 0 Diff 4/1
[2013-03-30 16:52:26] Accepted cbbd0e7e BFL 0 pool 0 Diff 1/1
[2013-03-30 16:52:28] Accepted 5c082b23 BFL 0 pool 0 Diff 2/1
[2013-03-30 16:52:34] Accepted 41bc1dee BFL 0 pool 0 Diff 3/1
[2013-03-30 16:52:38] Accepted 7933bd89 BFL 0 pool 0 Diff 2/1
[2013-03-30 16:53:04] Accepted 0d1a977d BFL 0 pool 0 Diff 19/15
[2013-03-30 16:53:05] Stratum from pool 0 requested work update
[2013-03-30 16:54:05] Stratum from pool 0 requested work update
[2013-03-30 16:55:05] Stratum from pool 0 requested work update
[2013-03-30 16:56:05] Stratum from pool 0 requested work update
[2013-03-30 16:57:05] Stratum from pool 0 requested work update
[2013-03-30 16:58:05] Stratum from pool 0 requested work update
[2013-03-30 16:58:13] Stratum from pool 0 detected new block
[2013-03-30 16:59:13] Stratum from pool 0 requested work update
[2013-03-30 17:00:13] Stratum from pool 0 requested work update
[2013-03-30 17:01:13] Stratum from pool 0 requested work update
[2013-03-30 17:01:23] Accepted 0cef40d4 BFL 0 pool 0 Diff 19/10