Id thought id give you my experience installing the latest beta 2.1.0.13
I've installed 2.1.0.13 over an existing 2.0.7.1 installation using the multicore launcher version.
Everything seems to work fine (the new installation resumed the calculation where the old version left off) and seems te be quicker

The traffic lights on all four clients show green.
Only one problem: The client does not show my cpu type (it says Unknown).
The old client reported EM64T Family 6 Model 23 Stepping 7 2666 MHz (Which I think is the correct ID)
The output from chkcpu32 is correct (see bellow)
CPU: Intel Q9450 on original clock speed
OS: Win XP (64 bits)
IE: Version 6 (I normaly use firefox latest version 3.5)
Mem: 4GB of DDRII RAM @1066MHz
CHKCPU32.exe output:
CPU Identification utility v2.04.059 beta (c) 1997-2009 Jan Steunebrink
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
CPU Vendor and Model: Intel Core 2 Quad Q8200-Q9550/QX9650/QX9770 C1-step
Internal CPU speed : 2667.0 MHz
System CPU count : 1 Physical CPU(s), 4 Core(s) per CPU, 4 Thread(s)
CPU-ID Vendor string: GenuineIntel
CPU-ID Name string : Intel(R) Core(TM)2 Quad CPU Q9450 @ 2.66GHz
CPU-ID Signature : 010677
CPU Features : Floating-Point Unit on chip : Yes
Time Stamp Counter : Yes
Enhanced SpeedStep Technology: Yes
Hyper-Threading Technology : No
Execute Disable protection : Yes
64-bit support : Yes
Virtualization Technology : Yes
Instr set extensions: MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1
Size of L1 cache : 64 KB
Integrated L2 cache : 6144 KB
Integrated L3 cache : None