I'll bet it's twice as hard with twins. Is it twice as hard? Or worse?

Truthful and complete answer:  It's too soon to tell.

Off-the-cuff and superficial answer:  Sort of.  But not really.

Obviously, there are things that are harder with two newborns at home.  But the overwhelming majority of adjustments that need to be made for two have already been made for one -- your first child, whether that's the older of twins or the oldest child in your family.  We found this to be true when we had Charlie.  When you have your first child, you pretty much give up your own childhood forever.  You stop being the center of your own life (at least most of the time, for most of us).  You give up a lot of the certainty that you will be able to control what kind of day you will have.  And that's not a sacrifice you can make twice.  You also lose the ability to choose whether to break off at will a relationship with another human being because "it's just not working out."  (Thankfully, most people get to practice making this sacrifice in the form of marriage before they're asked to do it with even greater permanency in parenthood.)  With your first child, there's some kind of loss of autonomy that needs to be grieved, and that's part of adjustment.  As I more succinctly put it to a friend expecting again, "Adding a second is more than twice the work, but on the bright side you really don't have any more personal freedom or autonomy left after the first so you might as well."  Trust me, when you get to your third and fourth, there's nothing left to grieve.

So, is it harder to have twins?  Yes.  But not as hard as you might think, and not as hard as some other things.

1. Rule 1:  A baby who is your first is harder than twins who aren't.  I don't care what people say about two kids being twice as hard as one.  Having two kids maybe twice as hard, but that doesn't mean the newborn is the problem.  Your first newborn is, barring complications or unusual illnesses, harder than all later babies.  I think Patrick's first diaper changes took somewhere on the order of 45 minutes, all told -- when I did them, that is. Obviously my time gradually improved, but there is absolutely nothing like the confidence that comes with your discovery that your precious child isn't made of glass. Assuming there's nothing particularly nasty about it, I can do both Anna and Evelyn's diaper changes in a total of maybe 2 minutes flat -- raise that to five if one of them has made things difficult, if you catch my drift, and I think you do.  And that's just one example.  All of the newborn problems are old hat, so far.  Even doing everything twice instead of once is nowhere near as hard as doing it for the first time.  Along these lines, people whose twins were their first birth have my undying respect.
2. Rule 2:  A baby who has colic or some other illness is harder than twins who don't.  Neither Patrick nor Charlie was colicky, but there were each more demanding in their own way than either Anna or Evelyn has turned out to be.  And we certainly know people whose newborns were horrendous.  (They turned into perfectly nice children, but you know what I'm saying here.)  Knock wood, neither of the girls has shown any tendency toward difficulty yet.  But I'm prepared to say that if one of them does, it will be that thing that makes this hard, not twins per se.
3. Rule 3:  A healthy baby who's spent time in the NICU is easier than one who hasn't.  Okay, this is not an argument for having a preterm birth, but the girls had a month of regimented lifestyle and have grown to expect to fall asleep without being mollycoddled, as Patrick and Charlie were.  It like sending your kid to a fancy boarding school before they develop behavior problems.  Obviously, this doesn't make it "better" than the fall-asleep-in-Mother's-arms personal attention -- in fact, quite the opposite, because we continue to think that style of parenting is more natural and better for the child -- but it does make parenting a newborn easier.  And, in the case of twins, it does more than make life easier, it makes it possible.  Put aside all romantic notions you have from your own singleton births.  You can't stand and bounce twins to sleep.  You can barely sit and rock them.  So while I'm not recommending time in the NICU, if you have twins and they don't happen to need intensive hospital care, I suggest you get your babies Ferberized by any means necessary.  It seems sick and wrong to take advantage of Anna and Evelyn's early time in isolettes in this way, but I simply do not know how it would be possible to manage two babies, both of whom insisted on being held to sleep.
4. Rule 4:  Twins of the same sex permit economies of scale.  If we had one boy and one girl, there would be problems of clothing, storage and decor that are avoided by having two babies of the same sex.  This makes it somewhat easier, as the babies can be kept in the same frilly bassinette and the same frilly onesies for as long as we like.  This doesn't make them as easy as one newborn, but it makes them easier than two newborns who are completely different from each other.

All told, there is more work, and it burdens a family in unexpected ways.  But it probably isn't quite as difficult as you fear, or, at least it isn't difficult in the ways you expect it to be.

Of course, in three weeks I'll probably be writing a detailed rebuttal to this post.  But for now, this is "doable."