I've been using these ferries for motorcycle trips abroad for over a decade, and still find them…read morebest overall for value, service and convenience.
The secret to good value is to book ahead: if you have a group booking, (often the case with motorcycles) this is best done over the phone as the website doesn't allow multiple bookings. Booked in January, a return crossing in July cost me just £46 per bike + passengers. (This is only £10 more than the price as a foot passenger!) Booking ahead applies to cars, too.
The staff are helpful and usually quick at loading bikes: they go on first, and deck-hands help secure them down. Newer ships (of both Seafrance and P&O) sometimes have special cradles for holding bikes, but when it's busy there aren't enough to go around, and so a traditional webbing brace is used, secured to floor anchors. I've never had a problem with this, even in very rough weather (but remember to put your alarm onto 'ferry' or 'service' modes, unless you want to irritate other passengers and flatten your battery). The only problem I've encountered is that the decks do get slippery in wet weather, but that affects all ferries, and I've not dropped the bike yet...
The timetable varies, but in high summer sailings leave roughly hourly, or better. The crossing takes about 90 minutes overall, but with the shops, bars and cafes, there's plenty to keep you occupied. For teenagers there's also a video-games room. But I prefer to be on deck: the Channel is the world's busiest shipping lane, so there's always something to see, if only the odd passing seagull! Note: the UK smoking ban means that smoking is now only allowed in designated outdoor deck areas.
Note also that passport control is undertaken at the port of departure - so UK passport control is at Calais. Allow at least 30 extra minutes for this when leaving France for the UK, as the UK checks are stringent, and therefore can be very slow in high season. Checks leaving the UK for France are rather quicker. Overall, I'd advise arriving 45 minutes ahead, just in case.
Also worth knowing is that, if you arrive earlier than your booked ferry, and there's room, they will let you travel on an earlier crossing at no extra cost. We returned recently over an hour earlier, and were waved straight onto the boat.
You could, of course, take a deep breath and pay to go via the Chunnel, which takes about 40 minutes (plus queuing time). But apart from losing the view, and the adventure, you'll pay at least double for an equivalent crossing.
***************************
NB: address and map are for the HQ office. The ferry port is clearly signposted at both Calais and Dover.