I only just noticed the availability of the 6.2.27 beta, so have not tried it, but have been trying the 6.2.25 version, installed in non-protected (ordinary) mode, on WinXP-32 SP3.
I only use "Advanced" view, and I haven't tweaked everything that's tweakable, so I am probably not the most thorough beta-tester.
No problem issues, but can the initial 2-minute delay be user-tuned? Waiting 2 minutes can be boring on the occasions when one wants to check that all is running well.

There may be a more serious problem with all BOINC versions, though: stuck downloads. A couple of months ago, I had exceeded my ISP's monthly download quota, and my download speed was being throttled to 64kbits/sec (1Mbit/sec uploads unaffected). While I was running several long bittorrent downloads, some, but not all, BOINC 6.2.18 downloads hung. I think I was able to restart them by exiting BOINC and restarting it. Meanwhile, the bittorrent client (µTorrent) carried on completely unfazed by this. Obviously its protocol is much more robust.
You may be able to simulate this situation by using a dial-up modem. (I have not tried that).
Because the message log is long, I have not included it here, but have uploaded it to: http://www.2shared.com/file/4292941/29ccded8/StuckDnloads080910.html