Hi
Zodiacs are nice well built boats that have a good reputation and pedegree, the new models (and possibly the older) have removable tubes so if the tube gets damaged it can be removed for repair fairly easilly, if your planning to tow arond a lot a 5.5 metre boat is a reasonable lenght, fairly light and will tow easilly and be easy to launch and recover, i'd go for the jocky seat lay out though as the bench seat or the silly stand up thing they supply wont be comfortable in anything less than a flat sea, you back will thank you for it i promise, (unless of course the boats all ready laid out as you've stipulated its been used as a demo !!, in which case i'd talk to the dealer as this seating adjustments can be made i believe)
Suzuki are a good solid engine and as its newish i'd assume its comming with a full warranty.