Many modern interfaces include mic preamps, and often have hardware compression and EQ for monitoring.  But there's still what seems like a healthy market for external mic preamps and channel strips to get a "golden signal" into the interface. 
 
There is a recent thread that suggests that the newer interfaces might have preamps that are as good or better than some older external units.
 
Do you think mic pres are important, or do you roll with what's handy?  (since handy might be quite dandy)
 
For my part, my interface doesn't have any pre's, but the external pre's I have strike me as better than the integrated ones I've tried. 

Most interfaces have decent pres and capture great sound.  External transformer-coupled mic pres provide a different sound and generally give more gain to play with.  Comps and EQs can be nice to for pre-shaping a sound.  Compression can even out a sound going in, compressing the difference between the loudest and softest levels, making it easier to mix.  Mostly I use high-pass filter but have a de-esser built in my channel strip and use that on vocals, esp. female.  Again, I don't go crazy but just a little shaving, a couple of dBs, making the sound more coherent and controllable in the mix (and thus leaving less work for the virtual effects).
 
The TASCAM UH-7000 has great preamps, but I still use external hardware going in through the line input for the most part.  Still,  to match some VO stuff from CA I'm using the 7000's brilliant and clear pres to better match the original recordings.  It is nice to have various tools. 

schwa
Many modern interfaces include mic preamps, and often have hardware compression and EQ for monitoring.  But there's still what seems like a healthy market for external mic preamps and channel strips to get a "golden signal" into the interface. 
 
There is a recent thread that suggests that the newer interfaces might have preamps that are as good or better than some older external units.
 
Do you think mic pres are important, or do you roll with what's handy?  (since handy might be quite dandy)
 
For my part, my interface doesn't have any pre's, but the external pre's I have strike me as better than the integrated ones I've tried. 

Most mic preamps from mid-priced interfaces to the higher price range will be decent and it will be hard to spot a difference, even when trying to some sort of A/B comparison ... yet, there some new units out there (like the most recent MOTU AVB units) with an almost shockingly low noise floor. it's incredible what these pre-amps resolve with clarity which would have previously been masked by higher noise floor (like drum room mics 3m away picking up the drummer scratching his ****) but if you want that masked, you can always later crank up the "noise" dial of some analogue emu plug-in.
 
As regards compression and EQ of modern interfaces ... well, great stuff to carve a near zero latency monitor mix using interface DSP rather than CPU but since these EQs/compressors are digital, I don't see the point of applying them to the recording. With all the plug-ins available you can do that later in a non-destructive manner.
 
Analogue pre-amps and channel strips are a different animal IMHO and despite the high quality of interface preamps will always have their place in a studio rack. I use them if I'm after a different sound e.g. various degrees of tube saturation, mild compression or EQ on the way into the DAW ...

The onboard mic preamps on mid to upper tier audio interfaces have been pretty decent for a good while.
That being said, if you compare a world-class mic preamp (Neve, GML, etc), you'll notice a difference.
It's like getting a mic upgrade across your entire collection.
 
ie:  The Neve Portico II sounds significantly better than the preamps on my Fireface UFX.
The sound is bigger/fuller, lower noise-floor, etc.
Mics that sound a bit strident with the RME preamps... sound more balanced with the Neve.
DI electric bass sounds far better.
This is not to say the UFX preamps are inherently bad or unusable (they're designed to function well at a given cost point).  The Neve is more of a "no compromise" design.  The sound reflects that... as does (unfortunately) the price.

and i think it's better to keep them separated than put them together...
 
modular makes more sense from a 'mix and match' perspective,
and from a maintenance perspective.
 
 

it really depends, IMO.  I agree with bat on the "modular mix and match"
 
I don't use EQ on the input ever.  I don't have any external EQ's.  I do use a compressor on the input most of the time, but I only compress lightly.  for compression I use an ART Pro VLA II or a dbx160.
 
the preamps on my MOTU (which is actually quite an old unit now) are really pretty decent for clean pres.  but I have other preamps I use specifically most of the time.  I have a True Systems preamp for when I want clean gain and I have a UAD-710 or an ART Pro MPA II for different "colors" of inputs that I can't get from the MOTU. 
 
so if all you need is clean gain and only software compression and EQ (which is what most audio interfaces use) then the preamps are pretty good and clean already, but if you want something a little different, go with outboard gear.

no substitute for a great pre.
Makes the rest of the job so much easier.
It's like using a knife- a dull knife will usually get the job done with added effort and mess.  
But a sharp, well-designed blade will have the best, and fastest results.
Wait, what were talking about?

exactly.
 

BlixYZ
no substitute for a great pre.
Makes the rest of the job so much easier.
It's like using a knife- a dull knife will usually get the job done with added effort and mess.  
But a sharp, well-designed blade will have the best, and fastest results.
Wait, what were talking about?

Thanks to everyone for their comments.
 
My interface doesn't have built in preamps, so I have always had to use outboard with my rig.  For many years, I used a pair of preamps that were decent at best. 
 
Last spring, I picked up an SSL preamp, and Blix's "sharp knife" metaphor rang true to my experience.  It somehow seemed to simplify things.  It's got 4 channels, and seems to handle whatever I plug into it well, where previously I sometimes had some trouble. 
 
I also just picked up a UA LA-610 (yesterday) for a price I could not refuse.  I'm interested to see if I can appreciate the "character/small EQ/slight compression" side of things.