Do you mean it will be good? Or bad?
We are a heavily loaded cruising cat but 8 knots is easy peezy, we regularly see 10 knots without really trying and speeds in the low teens are easily achievable with enough wind. But plus or minus 10 knots is comfortable and reduces stress on the boat - we're cruising, not racing. 
We moved from a monohull to a 46' cruising cat. It has LAR (low aspect ratio) keels rather than daggerboards, like the Catana range of cats, so it can dry out, much like a bilge keel mono. The space is, well, huge. Performance at anchor is superb. It's a much more stable platform for 'liveaboardability' and that stable platform also equates to much less crew fatigue on long passages. One particular occasion springs to mind that illustrates the point - we were sailing to windward in a pretty stiff breeze (I forget the numbers but it was a damn good '6') and we were standing there in the relative shelter of the cockpit drinking mugs of tea. We watched a 40 ish foot average & newish mono heading in the same direction that had crew clinging on and getting wet. Hour after hour of that on a mono or a cat? We prefer our cat thankyouverymuch. On another occasion, motoring up river, very strong wind against tide, we passed a Contessa 32 (not such a good comparison, I know) pounding into the waves and shifting some water over the decks. We were almost in disbelief because our cat was so stable and dry, although LWL would have played a part here. Nevertheless, we've sailed monos enough to know that a cruising cat is a world apart. I wouldn't go back to monos if I could help it.
As for the risk of capsize, well, it can happen, but thankfully it is relatively rare on cruising cats. Just like it is relatively rare for a mono to sink. Monos do sink, but that alone wouldn't stop me buying one. See above!
We are fortunate that our cat has excellent bridgedeck clearance and this reduces the likelihood of bridgedeck slamming. On the rare occasion it has happened, we are usually sailing close to the wind in pretty choppy conditions. Bearing away a few degrees stops it , and increases speed
The enemy of a catamaran is weight and it's an easy trap to fall into with all that space. For that reason I would consider 40' a minimum size for a couple who plan to liveaboard full time. If not full time then you can probably get away with something a little smaller.
Oh, yes, the other enemy of a catamaran is marinas who often charge mono + 50% rates although thankfully some charge standard rates and we make use of them where possible, although the long term plan is to spend more time at anchor as it's such a comfortable platform.
and we all know what these are worth! Fair winds
