I have the MCS singles on my 04 and do think they are a very nice quality shock, but I also think they are a definitely a harsher ride than you would get with stock. Even cranked down they are moderately aggressive, though that might be more a function of the spring rates than the damping. I have actually debating upgrading to the dual adjustable because I think you could get a better compromise out of them for the street with setting compression down to absorb the bumps, but keeping the rebound a bit higher so the wheel settles back down more slowly.
You'll certainly buy yourself more adjustability,
but it may not be in a range that matters to you for overall comfort on the street.
There are two additional thing you can adjust with the 2-ways over the 1-ways:
1. Compression
2. Canister pressures
For comfort (street driving), I generally run the compression settings at full soft or 1-click up from full soft. It only goes stiffer from there - one click makes a very noticeable difference. If full soft doesn't quite cut it, you can lower the canister pressures, but there's only so much that will do from my experience. FWIW, I've found that the factory fill of 175 psi seems to be the sweet spot for street driving, so again,
there really isn't as much adjustability as you might hope. As always, your mileage may vary.
And just so folks are aware, adjusting the canister pressure requires some additional equipment, and it isn't cheap - something along the lines of this:
SOLD OUT. See new and improved Shock Boss V2 here! Nitrogen Shock Inflator Kit 400 psi from Power Tank. The NIT-0400 Shock Filler Kit is the latest version of the industry's favorite on-the-go shock service kit. It will inflate shocks and bump stops up to 400 psi and all of the tools and...
powertank.com
You might be able to piece together something that's a little more affordable, but it will require some legwork. The biggest issue I've found is refilling the small nitrogen tank that comes in that kit (which is essentially a relabeled paintball marker tank, albeit a non-standard size). Any welding supply store will have nitrogen, but most won't have any clue how to fill the smaller tank. FYI, the Power Tank kit linked above includes the required adapter to fill it from any larger mother bottle with a standard size outlet valve (a CGA580 if I'm not mistaken). Those that can or will do it will look for the hydrostatic test date on the Power Tank bottle - once it goes out of hydro (5 years for aluminum tanks), you'll have to find a place to recertify it. Until then, they won't touch it. Paintball shops can do this, but most will likely outsource it to someone that regularly deals with fire extinguishers in your local area. I can assure you, it is a royal PITA, so much so that I ended up just buying my own small-ish (20 cu. ft.) nitrogen mother tank so I could do it myself and then just exchange the larger tanks when needed (and the welding supply company takes care of any hydro testing requirements on the larger tank). That was another ~$200, and is probably even more now.
You really do need a refill kit of some sort, because the extra lines and fittings that go along with the external canisters slowly leak over time, so it becomes a regular maintenance item (usually once per year/driving season).
That's a lot of words, so if you take away anything from my drivel, make it this:
Buyer beware, and try before you buy if at all possible to make sure that additional adjustability is worth it and will do what you need. 
