That is often the case in practice but the criterion as implemented in the code is the amount of work done -- it is a defence against exploits that attempt to lengthen the chain by artificially reducing the diff locally so more blocks can be mined.

Syncing does seem to take forever and my experience is that it often stops for a while (long enough for one to lose faith) and then just starts up again. I've synched from zero successfully with the Linux client (several times, just to convince myself that the first time wasn't a fluke) and with the OS X 10.6.8 client and the cross-compiled Windows client on wine.

For not entirely-unrelated reasons, I'm allowing a wine-hosted FantomFNX windows client to load from bootstrap and so far it's run all yesterday and all night, it's still going and has managed to load just over 100k blocks, that's significantly slower than the wine-hosted Slimcoin cross-compiled Windows client did synching from the live network. Can't speak for a natively-hosted client though.

Cheers

Graham