I've just had a session on Betfair and, while nothing crashed on me, I'd have to agree that the software is not the most stable. They did an upgrade this week (Tuesday I think) so there a probably are a few bugs in there.
Having said that, however, the competition is relatively soft (at the lower levels at least). If you're planning on just bonus-whoring it I'd say go for it!
I just cleared the Betfair bonus, and while I don't think I'll be playing much there, as i don't like the software much, I do believe it's a quite easy bonus to clear. I did it in four days or so 6-tabling 10 NL a couple of hours a day. It's was quite easy money and also a nice book bonus are comming my way, so I don't see any reason not to play on the site for the bonus. I might also add that I didn't have any trouble with their software unless you take into account the scheduled hours the site was down due to an update.
Lol I had problems with the software (alsways got 'connection lost' about 10 seconds after logging in to the software). So I already cashed out without clearing the bonus.
Can anyone advise another site? Has to be one of these: