I believe Bob Clearmountain said a very good thing about mix monitoring once. \"Check your mix on as many systems as you can before you commit\".
This has nothing to do with the quality of monitors IMHO but just a way of keeping your mix in perspective. Basically, when you are happy with a mix you shouldn't have a change of \"vibe\" in lack of a better word, when listening on another set of monitors or in a different room. While having mixed on a chosen pair of monitors for six hours or something and you feel the mix is more or less done... try switching to another pair and go crazy with the EQ a bit to see if you can get a \"musical enhancement\" somewhere on that pair and when you find that, switch back and try the same thing on your main pair. This is a great way of gaining musical perspective on a mix since you break out of your comfort zone.
With that said...
I think choosing your monitors is in a way dependent on what style of music you are going to mix. Basically, all monitors are good monitors but choosing your main pair can be a very important part of your workflow. I have worked mostly on Genelec 1032, 1031, 8030, 8040... Yamaha NS-10, Mackie HR824, Alesis Monitor One, Avantone MixCubes. From my experience (IMHO) I've found that the 1030 series works awful for me, never had a good mix on a pair of those. The 8000 series is a freakin' marble though! Doesn't sound like \"Genelec\" at all. Very very neutral sounding regardless of what room you put them in.. and that's a huge advantage and part of why they always seem to put out great mixes for people. NS-10s works like a charm but can be very dependent of the acoustics you put them in. Mackie HR824 likewise.. great monitors when put in the right space. In the wrong space.. they do sound awful. Alesis Monitor One good monitors for midrange sometimes, kind of like extended NS-10s. Avantone MixCubes, love these little suckers.. but can be very hard to get used to in the beginning. A great reference option to really hear what a mix sounds like in a worst case scenario.
Mixing on NS-10s and MixCubes is very cool but will never guarantee that your mix sounds really good on another set of monitors in another room. You have to understand why they work though.. because they do fill their purpose. Getting a mix to sound great on NS-10s or MixCubes (Auratones) will get you a very clean and separated midrange. Although this filled a much more important role when working mostly with analogue since the rest of the audio spectrum didn't get that very well represented by tape recorders anyway (subs and extreme high-end). So if you had a mix that sounded great on NS-10s or Auratones, it usually did sound great on other systems since you didn't have to pay that much attention to anything else. Times have changed though, and now it's more important than ever to understand what's going on down there and up here. Different musical styles utilize the available frequency space in very different ways, but what links them all together is the all important midrange. So getting a great mix of midrange in your music will get you in the ballpark but will not get it to sound perfect all year round.
I engineer a lot of electronica/dance as well as a lot of metal and hard rock. The difference in monitoring differ quite much between these genres. For instance, doing a rock mix on NS-10s will get you very close to what you want since it's more or less all about the midrange. Doing a dance mix on MixCubes though will get you a great midrange but will almost certainly sound awful on a big full range system. The other way around.. getting a super sounding dance mix on a full range system and then switching to a pair of MixCubes shall NOT change the vibe one bit. You should have the same sense of musicality, just not as extended.
So with all that mumbeling... I go for the school of thought that accurate monitoring will always be better. But have another pair of monitors handy (preferably something limited range) too gain perspective on what you are doing.