Just updated, and my ongoing GFN16MEGA task is still running :)
Also noticed a speed boost.
There is no chance that Boinc client give you ANY speed boost, because boinc client doesn't do any calculation. Application that do calculation wasn't changed :)
Hmmmmm, well I guess Yves (or stream) somehow gave me a speed boost for GFN of 2 hours :) :P
(it originally ran for 8.5 hours now 6.5hrs)
Well depending on your CPU and how old your version was on your old client... over the past few versions of BOINC a few CPU related improvements have been inserted for newer CPU's and the Processor Features of some CPU's have been corrected or updated.
Here is my CPU Feature string from Client boot
Processor features: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss htt tm pni ssse3 cx16 sse4_1 sse4_2 popcnt aes syscall nx lm vmx smx tm2 dca pbe
So under some conditions a newer Client could have given you a boost.