Other stuff...the biggest reason I reccomend liveaboard diving is that it's way lower effort. You set up you gear once, when you get on the boat, and wake up with a 30 foot walk to your gear (which is conveniently parked right over the dive site). You don't have to wake up in the morning, schlep all your stuff to the boat, set it up, ride to the dive, get off the boat for lunch...and...repeat in the afternoon.
And you don't have to dive. You can be lazy and sleep in, and make the second dive at the same site before the boat moves.
This pretty much sums up my main reasons for loving liveaboards. That, and the significantly higher number of dives per day, and better access to more remote sites. But I have spent a lot of time on boats, and my expectations may not be the same as some others who might want the sort of things resorts can offer (e.g. land-based sightseeing, more comfortable accommodations, access to restaurants in town, etc).
You're on a boat at sea for 7 days. For the next week, shoes are optional, everything you need is close at hand, and everything you don't need (TV, etc) is out of sight, out of mind. In between dives and meals, you can socialize, if you choose, or read, or sit and admire the sunset, or go take a nap.
Rough weather.... It's a judgment call for the Captain to determine when you keep trying to get some dives in, and when you have to turn tail and head for port or a sheltered mooring. From a guest's perspective, the most important thing is to keep your sense of adventure, and bear in mind that if bad weather spoils your diving, that's just the way it goes sometimes. Have the best time you can in spite of it all. A sense of adventure can come in handy here. Besides, if the weather is really that crappy, resort boats won't be diving either.
Being stuck with a jerk for the duration of the trip: Can happen, does happen, sucks, but it's not as bad as all that. Usually if there's a real jerk on board, most of the other people on board feel the same way about the person, and you just socialize with the people you DO like.
Food: I have yet to be on a liveaboard with =bad= food. Sometimes it's on par with diner food, rather than haute cuisine, but generally they provide a good selection of options that are reasonably well-prepared. Understand that the further you go from home, the greater the chances that the boat is depending on local supplies/ingredients and may not always have your favorite items available.
Limited space: Varies from boat to boat. Channel Islands, CA for example, all the liveaboards I'm aware of are dormitory style living. Guests stacked three bunks high, almost no space for your personal things, two heads shared by thirty divers, but you get by. Pack as light as you can, and carve out your little bit of personal space where you can. I MUCH prefer liveaboards that have private rooms, but even there, space tends to be tight, so packing light is a help. If tropical, you don't need more than t-shirts, shorts, maybe something with long sleeves for times when there might be a little chill.... Flip-flops are good for all occasions.
I love being at sea. I love waking up in the morning and walking out on deck and seeing the whole horizon, and the sun coming up over the ocean. I love rolling out of bed and knowing that as soon as breakfast is over, we'll be getting ready to get in the water. I love coming back from a dive with a hot cookie fresh from the oven waiting for me, and my room just a few short steps away. I love hanging out on the boat's sundeck with new and old friends. For me, there's no downside to liveaboard diving, but it depends what kind of vacation you're looking for. What I love might not be your idea of a good time, but if it is, you're going to love liveaboard diving.
. Met some GREAT people on every trip I have been on.
