CloudFlare on Spamhaus SBL (opens in new tab)

I recently got an message from a client who has a business email blocked because of a Spamhaus SBL listing for CloudFlare. I know they have already responded to this at http://blog.cloudflare.com/thoughts-on-abuse, but my client is paying them for speeding up their website, not to get blocked by an anti-spam filter. I see both sides of this, but the bottom line is that if they don;t resolve the problem with Spamhuas they will start to loose business starting with mine.

I've been a Cloudflare (paying) customer for less than a week and I can't say it's been a smooth ride. Are they usually worry-free or did I just add problems to my stack? I'd like to hear from people who've been using them for a while.