If I had to choose one word for Evolution, it would have to be "clunky".
You know how sometimes you're using Outlook and it does something stupid? And what it'll have done will be a typical "Microsoft mistake"? Their particularly speciality is bad error dialogs. Not only do they seem to put little effort into steering you away from troublesome behavior, when something does go wrong, they behave utterly idiotically.
They come up with a dialog saying "I've just thrown away this mail." with nothing but an "OK" button, and you shout "no, damn you, it's not okay!"
They come up with a dialog saying "Something went wrong. To fix it, you'll have to do A, B, and then C. And I'm just going to tell you this. It's not my job to do it."
They come up with a dialog saying "Something went wrong. It was either this, or that, or something else, or something else yet again. And I'm not going to make any effort to find out. Nor was there any real point me enumerating the possibilities, because I'm not going to even explain how to recover, let alone do anything for you."
You almost get the feeling there's a competition amongst Microsoft's programmers to come up with the worst, most offensive dialogs they can.
Evolution doesn't have that tendency. But there's something really, well, "clunky" about it. It reeks of C like a wino reeks of alcohol and urine.
It keeps blocking, for no obvious reason. Except maybe threads are "expensive" in some way. This is really irritating, and I can imagine they don't even notice. They're probably expecting it, and think it's fine. I've been guilty of that myself, but it doesn't take your users long to point out that there's something wrong. The authors should go away and use Apple's Mail or Microsoft's Outlook (or better still, Outlook Express, which was a great little mailer; the only Microsoft program I ever thought liked me). And when they come back, they'll be driven insane by the way that Evolution keeps stopping for no obvious reason. (And perhaps surprised to find that Outlook's constant slowness is less of a problem than Evolution's jerkiness. Predictability is important.)
Some of the interactions are far too awkward, and for no obvious reason. I've already talked about meeting requests, but name completion is another example. Apple and Microsoft both do this perfectly well. Their systems are different, but I work with both and have no problems. But Evolution keeps catching me out. It keeps turning underlined names back into non-underlined text. And it's far too stupid when it comes to guessing names. Outlook comes a respectable second here to Apple's Mail, which does a perfect job.
There's not enough reuse, presumably because C doesn't make it easy enough. Think the mail composer's name completion is bad? Check out the meeting request creator; it doesn't have any. You have to know and type out the full email address of the people you want to attend. Or you can open a dialog from which to choose names, which is a great showcase for how stupid the name-guessing is. It's laughably bad. You have to understand how lower-case letters are ordered after upper-case letters in ASCII to fully understand why it makes some of its more ridiculous guesses. (If it can't find a match, it chooses the ASCII-sorted 'next' entry.)
I'll give Evolution some credit for making an effort to interoperate with Outlook and Exchange (I wish Apple would do more in that area), but it really feels like a very early beta. I couldn't inflict it on my parents, for example.